Detailed Sudoku Solution example, based
on method of elimination.

Notation:
 there are 81 squares, denoted by two
 digits representing the row and column
 respectively.
 
 There are 9 boxes, numbered one to
 nine reading left-to-right-and-top-to-bottom.
 
 A fully determined digit is surrounded
 by asterisks.
 
 Numeric possibilities are noted in a
 3x3 arrangement in each square.

++===+===+===++===+===+===++===+===+===++
||   |   |***||***|   |   ||   |   |***||
||   |   |*7*||*2*|   |   ||   |   |*6*||
||   |   |***||***|   |   ||   |   |***||
++---+---+---++---+---+---++---+---+---++
||***|   |***||   |   |   ||   |   |   ||
||*5*|   |*4*||   |   |   ||   |   |   ||
||***|   |***||   |   |   ||   |   |   ||
++---+---+---++---+---+---++---+---+---++
||   |   |   ||   |***|***||***|   |   ||
||   |   |   ||   |*9*|*8*||*1*|   |   ||
||   |   |   ||   |***|***||***|   |   ||
++===+===+===++===+===+===++===+===+===++
||***|   |   ||   |***|***||   |   |   ||
||*6*|   |   ||   |*8*|*1*||   |   |   ||
||***|   |   ||   |***|***||   |   |   ||
++---+---+---++---+---+---++---+---+---++
||   |   |   ||   |   |   ||   |   |   ||
||   |   |   ||   |   |   ||   |   |   ||
||   |   |   ||   |   |   ||   |   |   ||
++---+---+---++---+---+---++---+---+---++
||   |   |   ||***|***|   ||   |   |***||
||   |   |   ||*4*|*6*|   ||   |   |*2*||
||   |   |   ||***|***|   ||   |   |***||
++===+===+===++===+===+===++===+===+===++
||   |   |***||***|***|   ||   |   |   ||
||   |   |*3*||*8 |*4*|   ||   |   |   ||
||   |   |***||***|***|   ||   |   |   ||
++---+---+---++---+---+---++---+---+---++
||   |   |   ||   |   |   ||***|   |***||
||   |   |   ||   |   |   ||*9*|   |*1*||
||   |   |   ||   |   |   ||***|   |***||
++---+---+---++---+---+---++---+---+---++
||***|   |   ||   |   |***||***|   |   ||
||*8*|   |   ||   |   |*6*||*5*|   |   ||
||***|   |   ||   |   |***||***|   |   ||
++===+===+===++===+===+===++===+===+===++

Filling in all possible numbers...

++===+===+===++===+===+===++===+===+===++
||1 3|1 3|***||***|1 3|  3||  3|  3|***||
||   |   |*7*||*2*| 5 |45 ||4  |45 |*6*||
||  9| 89|***||***|   |   || 8 | 89|***||
++---+---+---++---+---+---++---+---+---++
||***|123|***||1 3|1 3|  3|| 23| 23|  3||
||*5*|  6|*4*||  6|   |   ||   |   |   ||
||***| 89|***||7  |7  |7  ||78 |789|789||
++---+---+---++---+---+---++---+---+---++
|| 23| 23| 2 ||  3|***|***||***| 23|  3||
||   |  6|  6|| 56|*9*|*8*||*1*|45 |45 ||
||   |   |   ||7  |***|***||***|7  |7  ||
++===+===+===++===+===+===++===+===+===++
||***| 23| 2 ||  3|***|***||  3|  3|  3||
||*6*|45 | 5 || 5 |*8*|*1*||4  |45 |45 ||
||***|7 9|  9||7 9|***|***||7  |7 9|7 9||
++---+---+---++---+---+---++---+---+---++
||123|123|12 ||  3| 23| 23||   |1 3|  3||
||4  |45 | 5 || 5 | 5 | 5 ||4 6|456|45 ||
||7 9|789| 89||7 9|7  |7 9||78 |789|789||
++---+---+---++---+---+---++---+---+---++
||1 3|1 3|1  ||***|***|  3||  3|1 3|***||
||   | 5 | 5 ||*4*|*6*| 5 ||   | 5 |*2*||
||7 9|789| 89||***|***|7 9||78 |789|***||
++===+===+===++===+===+===++===+===+===++
||12 |12 |***||***|***| 2 || 2 | 2 |   ||
||   | 56|*3*||*8*|*4*| 5 ||  6|  6|   ||
||7 9|7 9|***||***|***|7 9||7  |7  |7  ||
++---+---+---++---+---+---++---+---+---++
|| 2 | 2 | 2 ||  3| 23| 23||***| 23|***||
||4  |456| 56|| 5 | 5 | 5 ||*9*|4 6|*1*||
||7  |7  |   ||7  |7  |7  ||***|78 |***||
++---+---+---++---+---+---++---+---+---++
||***|12 |12 ||1 3|123|***||***| 23|  3||
||*8*|4  |   ||   |   |*6*||*5*|4  |4  ||
||***|7 9|  9||7 9|7  |***||***|7  |7  ||
++===+===+===++===+===+===++===+===+===++

square 79 has only a 7... now known, and
can eliminate all 7s in row 7, column 9,
and box 9.  This is a "naked 7".

++===+===+===++===+===+===++===+===+===++
||1 3|1 3|***||***|1 3|  3||  3|  3|***||
||   |   |*7*||*2*| 5 |45 ||4  |45 |*6*||
||  9| 89|***||***|   |   || 8 | 89|***||
++---+---+---++---+---+---++---+---+---++
||***|123|***||1 3|1 3|  3|| 23| 23|  3||
||*5*|  6|*4*||  6|   |   ||   |   |   ||
||***| 89|***||7  |7  |7  ||78 |789| 89||
++---+---+---++---+---+---++---+---+---++
|| 23| 23| 2 ||  3|***|***||***| 23|  3||
||   |  6|  6|| 56|*9*|*8*||*1*|45 |45 ||
||   |   |   ||7  |***|***||***|7  |   ||
++===+===+===++===+===+===++===+===+===++
||***| 23| 2 ||  3|***|***||  3|  3|  3||
||*6*|45 | 5 || 5 |*8*|*1*||4  |45 |45 ||
||***|7 9|  9||7 9|***|***||7  |7 9|  9||
++---+---+---++---+---+---++---+---+---++
||123|123|12 ||  3| 23| 23||   |1 3|  3||
||4  |45 | 5 || 5 | 5 | 5 ||4 6|456|45 ||
||7 9|789| 89||7 9|7  |7 9||78 |789| 89||
++---+---+---++---+---+---++---+---+---++
||1 3|1 3|1  ||***|***|  3||  3|1 3|***||
||   | 5 | 5 ||*4*|*6*| 5 ||   | 5 |*2*||
||7 9|789| 89||***|***|7 9||78 |789|***||
++===+===+===++===+===+===++===+===+===++
||12 |12 |***||***|***| 2 || 2 | 2 |***||
||   | 56|*3*||*8*|*4*| 5 ||  6|  6|*7*||
||  9|  9|***||***|***|  9||   |   |***||
++---+---+---++---+---+---++---+---+---++
|| 2 | 2 | 2 ||  3| 23| 23||***| 23|***||
||4  |456| 56|| 5 | 5 | 5 ||*9*|4 6|*1*||
||7  |7  |   ||7  |7  |7  ||***| 8 |***||
++---+---+---++---+---+---++---+---+---++
||***|12 |12 ||1 3|123|***||***| 23|  3||
||*8*|4  |   ||   |   |*6*||*5*|4  |4  ||
||***|7 9|  9||7 9|7  |***||***|   |   ||
++===+===+===++===+===+===++===+===+===++

square 77 and 78 have 2 and 6... neither
2 nor 6 can occur elsewhere in box 9 or
in row 7. This is a "naked pair".

++===+===+===++===+===+===++===+===+===++
||1 3|1 3|***||***|1 3|  3||  3|  3|***||
||   |   |*7*||*2*| 5 |45 ||4  |45 |*6*||
||  9| 89|***||***|   |   || 8 | 89|***||
++---+---+---++---+---+---++---+---+---++
||***|123|***||1 3|1 3|  3|| 23| 23|  3||
||*5*|  6|*4*||  6|   |   ||   |   |   ||
||***| 89|***||7  |7  |7  ||78 |789| 89||
++---+---+---++---+---+---++---+---+---++
|| 23| 23| 2 ||  3|***|***||***| 23|  3||
||   |  6|  6|| 56|*9*|*8*||*1*|45 |45 ||
||   |   |   ||7  |***|***||***|7  |   ||
++===+===+===++===+===+===++===+===+===++
||***| 23| 2 ||  3|***|***||  3|  3|  3||
||*6*|45 | 5 || 5 |*8*|*1*||4  |45 |45 ||
||***|7 9|  9||7 9|***|***||7  |7 9|  9||
++---+---+---++---+---+---++---+---+---++
||123|123|12 ||  3| 23| 23||   |1 3|  3||
||4  |45 | 5 || 5 | 5 | 5 ||4 6|456|45 ||
||7 9|789| 89||7 9|7  |7 9||78 |789| 89||
++---+---+---++---+---+---++---+---+---++
||1 3|1 3|1  ||***|***|  3||  3|1 3|***||
||   | 5 | 5 ||*4*|*6*| 5 ||   | 5 |*2*||
||7 9|789| 89||***|***|7 9||78 |789|***||
++===+===+===++===+===+===++===+===+===++
||1  |1  |***||***|***|   || 2 | 2 |***||
||   | 5 |*3*||*8*|*4*| 5 ||  6|  6|*7*||
||  9|  9|***||***|***|  9||   |   |***||
++---+---+---++---+---+---++---+---+---++
|| 2 | 2 | 2 ||  3| 23| 23||***|  3|***||
||4  |456| 56|| 5 | 5 | 5 ||*9*|4  |*1*||
||7  |7  |   ||7  |7  |7  ||***| 8 |***||
++---+---+---++---+---+---++---+---+---++
||***|12 |12 ||1 3|123|***||***|  3|  3||
||*8*|4  |   ||   |   |*6*||*5*|4  |4  ||
||***|7 9|  9||7 9|7  |***||***|   |   ||
++===+===+===++===+===+===++===+===+===++

Naked pair 3 and 4 in squares 98 and 99,
so 3 and 4 cannot appear elsewhere in
box 9 or row 9

++===+===+===++===+===+===++===+===+===++
||1 3|1 3|***||***|1 3|  3||  3|  3|***||
||   |   |*7*||*2*| 5 |45 ||4  |45 |*6*||
||  9| 89|***||***|   |   || 8 | 89|***||
++---+---+---++---+---+---++---+---+---++
||***|123|***||1 3|1 3|  3|| 23| 23|  3||
||*5*|  6|*4*||  6|   |   ||   |   |   ||
||***| 89|***||7  |7  |7  ||78 |789| 89||
++---+---+---++---+---+---++---+---+---++
|| 23| 23| 2 ||  3|***|***||***| 23|  3||
||   |  6|  6|| 56|*9*|*8*||*1*|45 |45 ||
||   |   |   ||7  |***|***||***|7  |   ||
++===+===+===++===+===+===++===+===+===++
||***| 23| 2 ||  3|***|***||  3|  3|  3||
||*6*|45 | 5 || 5 |*8*|*1*||4  |45 |45 ||
||***|7 9|  9||7 9|***|***||7  |7 9|  9||
++---+---+---++---+---+---++---+---+---++
||123|123|12 ||  3| 23| 23||   |1 3|  3||
||4  |45 | 5 || 5 | 5 | 5 ||4 6|456|45 ||
||7 9|789| 89||7 9|7  |7 9||78 |789| 89||
++---+---+---++---+---+---++---+---+---++
||1 3|1 3|1  ||***|***|  3||  3|1 3|***||
||   | 5 | 5 ||*4*|*6*| 5 ||   | 5 |*2*||
||7 9|789| 89||***|***|7 9||78 |789|***||
++===+===+===++===+===+===++===+===+===++
||1  |1  |***||***|***|   || 2 | 2 |***||
||   | 5 |*3*||*8*|*4*| 5 ||  6|  6|*7*||
||  9|  9|***||***|***|  9||   |   |***||
++---+---+---++---+---+---++---+---+---++
|| 2 | 2 | 2 ||  3| 23| 23||***|   |***||
||4  |456| 56|| 5 | 5 | 5 ||*9*|   |*1*||
||7  |7  |   ||7  |7  |7  ||***| 8 |***||
++---+---+---++---+---+---++---+---+---++
||***|12 |12 ||1  |12 |***||***|  3|  3||
||*8*|   |   ||   |   |*6*||*5*|4  |4  ||
||***|7 9|  9||7 9|7  |***||***|   |   ||
++===+===+===++===+===+===++===+===+===++

square 88 is now known to have an 8, so
clear row 8 and column 8... ("naked 8")

++===+===+===++===+===+===++===+===+===++
||1 3|1 3|***||***|1 3|  3||  3|  3|***||
||   |   |*7*||*2*| 5 |45 ||4  |45 |*6*||
||  9| 89|***||***|   |   || 8 |  9|***||
++---+---+---++---+---+---++---+---+---++
||***|123|***||1 3|1 3|  3|| 23| 23|  3||
||*5*|  6|*4*||  6|   |   ||   |   |   ||
||***| 89|***||7  |7  |7  ||78 |7 9| 89||
++---+---+---++---+---+---++---+---+---++
|| 23| 23| 2 ||  3|***|***||***| 23|  3||
||   |  6|  6|| 56|*9*|*8*||*1*|45 |45 ||
||   |   |   ||7  |***|***||***|7  |   ||
++===+===+===++===+===+===++===+===+===++
||***| 23| 2 ||  3|***|***||  3|  3|  3||
||*6*|45 | 5 || 5 |*8*|*1*||4  |45 |45 ||
||***|7 9|  9||7 9|***|***||7  |7 9|  9||
++---+---+---++---+---+---++---+---+---++
||123|123|12 ||  3| 23| 23||   |1 3|  3||
||4  |45 | 5 || 5 | 5 | 5 ||4 6|456|45 ||
||7 9|789| 89||7 9|7  |7 9||78 |7 9| 89||
++---+---+---++---+---+---++---+---+---++
||1 3|1 3|1  ||***|***|  3||  3|1 3|***||
||   | 5 | 5 ||*4*|*6*| 5 ||   | 5 |*2*||
||7 9|789| 89||***|***|7 9||78 |7 9|***||
++===+===+===++===+===+===++===+===+===++
||1  |1  |***||***|***|   || 2 | 2 |***||
||   | 5 |*3*||*8*|*4*| 5 ||  6|  6|*7*||
||  9|  9|***||***|***|  9||   |   |***||
++---+---+---++---+---+---++---+---+---++
|| 2 | 2 | 2 ||  3| 23| 23||***|***|***||
||4  |456| 56|| 5 | 5 | 5 ||*9*|*8*|*1*||
||7  |7  |   ||7  |7  |7  ||***|***|***||
++---+---+---++---+---+---++---+---+---++
||***|12 |12 ||1  |12 |***||***|  3|  3||
||*8*|   |   ||   |   |*6*||*5*|4  |4  ||
||***|7 9|  9||7 9|7  |***||***|   |   ||
++===+===+===++===+===+===++===+===+===++

squares 31, 32, and 33 contain only three
digits, so those digits cannot appear elsewhere
in box 1 or row 3 ("naked triplet")

++===+===+===++===+===+===++===+===+===++
||1  |1  |***||***|1 3|  3||  3|  3|***||
||   |   |*7*||*2*| 5 |45 ||4  |45 |*6*||
||  9| 89|***||***|   |   || 8 |  9|***||
++---+---+---++---+---+---++---+---+---++
||***|1  |***||1 3|1 3|  3|| 23| 23|  3||
||*5*|   |*4*||  6|   |   ||   |   |   ||
||***| 89|***||7  |7  |7  ||78 |7 9| 89||
++---+---+---++---+---+---++---+---+---++
|| 23| 23| 2 ||   |***|***||***|   |   ||
||   |  6|  6|| 5 |*9*|*8*||*1*|45 |45 ||
||   |   |   ||7  |***|***||***|7  |   ||
++===+===+===++===+===+===++===+===+===++
||***| 23| 2 ||  3|***|***||  3|  3|  3||
||*6*|45 | 5 || 5 |*8*|*1*||4  |45 |45 ||
||***|7 9|  9||7 9|***|***||7  |7 9|  9||
++---+---+---++---+---+---++---+---+---++
||123|123|12 ||  3| 23| 23||   |1 3|  3||
||4  |45 | 5 || 5 | 5 | 5 ||4 6|456|45 ||
||7 9|789| 89||7 9|7  |7 9||78 |7 9| 89||
++---+---+---++---+---+---++---+---+---++
||1 3|1 3|1  ||***|***|  3||  3|1 3|***||
||   | 5 | 5 ||*4*|*6*| 5 ||   | 5 |*2*||
||7 9|789| 89||***|***|7 9||78 |7 9|***||
++===+===+===++===+===+===++===+===+===++
||1  |1  |***||***|***|   || 2 | 2 |***||
||   | 5 |*3*||*8*|*4*| 5 ||  6|  6|*7*||
||  9|  9|***||***|***|  9||   |   |***||
++---+---+---++---+---+---++---+---+---++
|| 2 | 2 | 2 ||  3| 23| 23||***|***|***||
||4  |456| 56|| 5 | 5 | 5 ||*9*|*8*|*1*||
||7  |7  |   ||7  |7  |7  ||***|***|***||
++---+---+---++---+---+---++---+---+---++
||***|12 |12 ||1  |12 |***||***|  3|  3||
||*8*|   |   ||   |   |*6*||*5*|4  |4  ||
||***|7 9|  9||7 9|7  |***||***|   |   ||
++===+===+===++===+===+===++===+===+===++

squares 15, 34, 25, and 26 contain
1,3,5 and 7, so these cannot appear
elsewhere in box 2 ("naked quad")

++===+===+===++===+===+===++===+===+===++
||1  |1  |***||***|1 3|   ||  3|  3|***||
||   |   |*7*||*2*| 5 |4  ||4  |45 |*6*||
||  9| 89|***||***|   |   || 8 |  9|***||
++---+---+---++---+---+---++---+---+---++
||***|1  |***||   |1 3|  3|| 23| 23|  3||
||*5*|   |*4*||  6|   |   ||   |   |   ||
||***| 89|***||   |7  |7  ||78 |7 9| 89||
++---+---+---++---+---+---++---+---+---++
|| 23| 23| 2 ||   |***|***||***|   |   ||
||   |  6|  6|| 5 |*9*|*8*||*1*|45 |45 ||
||   |   |   ||7  |***|***||***|7  |   ||
++===+===+===++===+===+===++===+===+===++
||***| 23| 2 ||  3|***|***||  3|  3|  3||
||*6*|45 | 5 || 5 |*8*|*1*||4  |45 |45 ||
||***|7 9|  9||7 9|***|***||7  |7 9|  9||
++---+---+---++---+---+---++---+---+---++
||123|123|12 ||  3| 23| 23||   |1 3|  3||
||4  |45 | 5 || 5 | 5 | 5 ||4 6|456|45 ||
||7 9|789| 89||7 9|7  |7 9||78 |7 9| 89||
++---+---+---++---+---+---++---+---+---++
||1 3|1 3|1  ||***|***|  3||  3|1 3|***||
||   | 5 | 5 ||*4*|*6*| 5 ||   | 5 |*2*||
||7 9|789| 89||***|***|7 9||78 |7 9|***||
++===+===+===++===+===+===++===+===+===++
||1  |1  |***||***|***|   || 2 | 2 |***||
||   | 5 |*3*||*8*|*4*| 5 ||  6|  6|*7*||
||  9|  9|***||***|***|  9||   |   |***||
++---+---+---++---+---+---++---+---+---++
|| 2 | 2 | 2 ||  3| 23| 23||***|***|***||
||4  |456| 56|| 5 | 5 | 5 ||*9*|*8*|*1*||
||7  |7  |   ||7  |7  |7  ||***|***|***||
++---+---+---++---+---+---++---+---+---++
||***|12 |12 ||1  |12 |***||***|  3|  3||
||*8*|   |   ||   |   |*6*||*5*|4  |4  ||
||***|7 9|  9||7 9|7  |***||***|   |   ||
++===+===+===++===+===+===++===+===+===++

Naked 6 in square 24. No consequent
eliminations from this.

However, square 16 has been reduced to 4,
and there are eliminations of digit 4
in row 1.

++===+===+===++===+===+===++===+===+===++
||1  |1  |***||***|1 3|***||  3|  3|***||
||   |   |*7*||*2*| 5 |*4*||   | 5 |*6*||
||  9| 89|***||***|   |***|| 8 |  9|***||
++---+---+---++---+---+---++---+---+---++
||***|1  |***||***|1 3|  3|| 23| 23|  3||
||*5*|   |*4*||*6*|   |   ||   |   |   ||
||***| 89|***||***|7  |7  ||78 |7 9| 89||
++---+---+---++---+---+---++---+---+---++
|| 23| 23| 2 ||   |***|***||***|   |   ||
||   |  6|  6|| 5 |*9*|*8*||*1*|45 |45 ||
||   |   |   ||7  |***|***||***|7  |   ||
++===+===+===++===+===+===++===+===+===++
||***| 23| 2 ||  3|***|***||  3|  3|  3||
||*6*|45 | 5 || 5 |*8*|*1*||4  |45 |45 ||
||***|7 9|  9||7 9|***|***||7  |7 9|  9||
++---+---+---++---+---+---++---+---+---++
||123|123|12 ||  3| 23| 23||   |1 3|  3||
||4  |45 | 5 || 5 | 5 | 5 ||4 6|456|45 ||
||7 9|789| 89||7 9|7  |7 9||78 |7 9| 89||
++---+---+---++---+---+---++---+---+---++
||1 3|1 3|1  ||***|***|  3||  3|1 3|***||
||   | 5 | 5 ||*4*|*6*| 5 ||   | 5 |*2*||
||7 9|789| 89||***|***|7 9||78 |7 9|***||
++===+===+===++===+===+===++===+===+===++
||1  |1  |***||***|***|   || 2 | 2 |***||
||   | 5 |*3*||*8*|*4*| 5 ||  6|  6|*7*||
||  9|  9|***||***|***|  9||   |   |***||
++---+---+---++---+---+---++---+---+---++
|| 2 | 2 | 2 ||  3| 23| 23||***|***|***||
||4  |456| 56|| 5 | 5 | 5 ||*9*|*8*|*1*||
||7  |7  |   ||7  |7  |7  ||***|***|***||
++---+---+---++---+---+---++---+---+---++
||***|12 |12 ||1  |12 |***||***|  3|  3||
||*8*|   |   ||   |   |*6*||*5*|4  |4  ||
||***|7 9|  9||7 9|7  |***||***|   |   ||
++===+===+===++===+===+===++===+===+===++

In column 7, the number 4 only occurs in
box 6.  Therefore, 4 cannot occur elsewhere
in box 6.

++===+===+===++===+===+===++===+===+===++
||1  |1  |***||***|1 3|***||  3|  3|***||
||   |   |*7*||*2*| 5 |*4*||   | 5 |*6*||
||  9| 89|***||***|   |***|| 8 |  9|***||
++---+---+---++---+---+---++---+---+---++
||***|1  |***||***|1 3|  3|| 23| 23|  3||
||*5*|   |*4*||*6*|   |   ||   |   |   ||
||***| 89|***||***|7  |7  ||78 |7 9| 89||
++---+---+---++---+---+---++---+---+---++
|| 23| 23| 2 ||   |***|***||***|   |   ||
||   |  6|  6|| 5 |*9*|*8*||*1*|45 |45 ||
||   |   |   ||7  |***|***||***|7  |   ||
++===+===+===++===+===+===++===+===+===++
||***| 23| 2 ||  3|***|***||  3|  3|  3||
||*6*|45 | 5 || 5 |*8*|*1*||4  | 5 | 5 ||
||***|7 9|  9||7 9|***|***||7  |7 9|  9||
++---+---+---++---+---+---++---+---+---++
||123|123|12 ||  3| 23| 23||   |1 3|  3||
||4  |45 | 5 || 5 | 5 | 5 ||4 6| 56| 5 ||
||7 9|789| 89||7 9|7  |7 9||78 |7 9| 89||
++---+---+---++---+---+---++---+---+---++
||1 3|1 3|1  ||***|***|  3||  3|1 3|***||
||   | 5 | 5 ||*4*|*6*| 5 ||   | 5 |*2*||
||7 9|789| 89||***|***|7 9||78 |7 9|***||
++===+===+===++===+===+===++===+===+===++
||1  |1  |***||***|***|   || 2 | 2 |***||
||   | 5 |*3*||*8*|*4*| 5 ||  6|  6|*7*||
||  9|  9|***||***|***|  9||   |   |***||
++---+---+---++---+---+---++---+---+---++
|| 2 | 2 | 2 ||  3| 23| 23||***|***|***||
||4  |456| 56|| 5 | 5 | 5 ||*9*|*8*|*1*||
||7  |7  |   ||7  |7  |7  ||***|***|***||
++---+---+---++---+---+---++---+---+---++
||***|12 |12 ||1  |12 |***||***|  3|  3||
||*8*|   |   ||   |   |*6*||*5*|4  |4  ||
||***|7 9|  9||7 9|7  |***||***|   |   ||
++===+===+===++===+===+===++===+===+===++

In column 4, number 1 only occurs in square 94,
so 7 and 9 can be removed from that square,
and 1 can be cleared elsewhere in row 9.
("hidden 1")

++===+===+===++===+===+===++===+===+===++
||1  |1  |***||***|1 3|***||  3|  3|***||
||   |   |*7*||*2*| 5 |*4*||   | 5 |*6*||
||  9| 89|***||***|   |***|| 8 |  9|***||
++---+---+---++---+---+---++---+---+---++
||***|1  |***||***|1 3|  3|| 23| 23|  3||
||*5*|   |*4*||*6*|   |   ||   |   |   ||
||***| 89|***||***|7  |7  ||78 |7 9| 89||
++---+---+---++---+---+---++---+---+---++
|| 23| 23| 2 ||   |***|***||***|   |   ||
||   |  6|  6|| 5 |*9*|*8*||*1*|45 |45 ||
||   |   |   ||7  |***|***||***|7  |   ||
++===+===+===++===+===+===++===+===+===++
||***| 23| 2 ||  3|***|***||  3|  3|  3||
||*6*|45 | 5 || 5 |*8*|*1*||4  | 5 | 5 ||
||***|7 9|  9||7 9|***|***||7  |7 9|  9||
++---+---+---++---+---+---++---+---+---++
||123|123|12 ||  3| 23| 23||   |1 3|  3||
||4  |45 | 5 || 5 | 5 | 5 ||4 6| 56| 5 ||
||7 9|789| 89||7 9|7  |7 9||78 |7 9| 89||
++---+---+---++---+---+---++---+---+---++
||1 3|1 3|1  ||***|***|  3||  3|1 3|***||
||   | 5 | 5 ||*4*|*6*| 5 ||   | 5 |*2*||
||7 9|789| 89||***|***|7 9||78 |7 9|***||
++===+===+===++===+===+===++===+===+===++
||1  |1  |***||***|***|   || 2 | 2 |***||
||   | 5 |*3*||*8*|*4*| 5 ||  6|  6|*7*||
||  9|  9|***||***|***|  9||   |   |***||
++---+---+---++---+---+---++---+---+---++
|| 2 | 2 | 2 ||  3| 23| 23||***|***|***||
||4  |456| 56|| 5 | 5 | 5 ||*9*|*8*|*1*||
||7  |7  |   ||7  |7  |7  ||***|***|***||
++---+---+---++---+---+---++---+---+---++
||***| 2 | 2 ||***| 2 |***||***|  3|  3||
||*8*|   |   ||*1*|   |*6*||*5*|4  |4  ||
||***|7 9|  9||***|7  |***||***|   |   ||
++===+===+===++===+===+===++===+===+===++

In squares 33, 34, 38 and 39, only digits
2, 5, 6, and 9 appear (naked quad or hidden
pair 1 and 8).

++===+===+===++===+===+===++===+===+===++
||1  |1  |***||***|1 3|***||  3|  3|***||
||   |   |*7*||*2*| 5 |*4*||   | 5 |*6*||
||  9| 89|***||***|   |***|| 8 |  9|***||
++---+---+---++---+---+---++---+---+---++
||***|1  |***||***|1 3|  3|| 23| 23|  3||
||*5*|   |*4*||*6*|   |   ||   |   |   ||
||***| 89|***||***|7  |7  ||78 |7 9| 89||
++---+---+---++---+---+---++---+---+---++
|| 23| 23| 2 ||   |***|***||***|   |   ||
||   |  6|  6|| 5 |*9*|*8*||*1*|45 |45 ||
||   |   |   ||7  |***|***||***|7  |   ||
++===+===+===++===+===+===++===+===+===++
||***| 23| 2 ||  3|***|***||  3|  3|  3||
||*6*|45 | 5 || 5 |*8*|*1*||4  | 5 | 5 ||
||***|7 9|  9||7 9|***|***||7  |7 9|  9||
++---+---+---++---+---+---++---+---+---++
||123|123|1  ||  3| 23| 23||   |1 3|  3||
||4  |45 |   || 5 | 5 | 5 ||4 6| 56| 5 ||
||7 9|789| 8 ||7 9|7  |7 9||78 |7 9| 89||
++---+---+---++---+---+---++---+---+---++
||1 3|1 3|1  ||***|***|  3||  3|1 3|***||
||   | 5 |   ||*4*|*6*| 5 ||   | 5 |*2*||
||7 9|789| 8 ||***|***|7 9||78 |7 9|***||
++===+===+===++===+===+===++===+===+===++
||1  |1  |***||***|***|   || 2 | 2 |***||
||   | 5 |*3*||*8*|*4*| 5 ||  6|  6|*7*||
||  9|  9|***||***|***|  9||   |   |***||
++---+---+---++---+---+---++---+---+---++
|| 2 | 2 | 2 ||  3| 23| 23||***|***|***||
||4  |456| 56|| 5 | 5 | 5 ||*9*|*8*|*1*||
||7  |7  |   ||7  |7  |7  ||***|***|***||
++---+---+---++---+---+---++---+---+---++
||***| 2 | 2 ||***| 2 |***||***|  3|  3||
||*8*|   |   ||*1*|   |*6*||*5*|4  |4  ||
||***|7 9|  9||***|7  |***||***|   |   ||
++===+===+===++===+===+===++===+===+===++

Pair 1 and 8 in squares 34 and 35 mean
those digits cannot appear elsewhere in
box 4.

++===+===+===++===+===+===++===+===+===++
||1  |1  |***||***|1 3|***||  3|  3|***||
||   |   |*7*||*2*| 5 |*4*||   | 5 |*6*||
||  9| 89|***||***|   |***|| 8 |  9|***||
++---+---+---++---+---+---++---+---+---++
||***|1  |***||***|1 3|  3|| 23| 23|  3||
||*5*|   |*4*||*6*|   |   ||   |   |   ||
||***| 89|***||***|7  |7  ||78 |7 9| 89||
++---+---+---++---+---+---++---+---+---++
|| 23| 23| 2 ||   |***|***||***|   |   ||
||   |  6|  6|| 5 |*9*|*8*||*1*|45 |45 ||
||   |   |   ||7  |***|***||***|7  |   ||
++===+===+===++===+===+===++===+===+===++
||***| 23| 2 ||  3|***|***||  3|  3|  3||
||*6*|45 | 5 || 5 |*8*|*1*||4  | 5 | 5 ||
||***|7 9|  9||7 9|***|***||7  |7 9|  9||
++---+---+---++---+---+---++---+---+---++
|| 23| 23|1  ||  3| 23| 23||   |1 3|  3||
||4  |45 |   || 5 | 5 | 5 ||4 6| 56| 5 ||
||7 9|7 9| 8 ||7 9|7  |7 9||78 |7 9| 89||
++---+---+---++---+---+---++---+---+---++
||  3|  3|1  ||***|***|  3||  3|1 3|***||
||   | 5 |   ||*4*|*6*| 5 ||   | 5 |*2*||
||7 9|7 9| 8 ||***|***|7 9||78 |7 9|***||
++===+===+===++===+===+===++===+===+===++
||1  |1  |***||***|***|   || 2 | 2 |***||
||   | 5 |*3*||*8*|*4*| 5 ||  6|  6|*7*||
||  9|  9|***||***|***|  9||   |   |***||
++---+---+---++---+---+---++---+---+---++
|| 2 | 2 | 2 ||  3| 23| 23||***|***|***||
||4  |456| 56|| 5 | 5 | 5 ||*9*|*8*|*1*||
||7  |7  |   ||7  |7  |7  ||***|***|***||
++---+---+---++---+---+---++---+---+---++
||***| 2 | 2 ||***| 2 |***||***|  3|  3||
||*8*|   |   ||*1*|   |*6*||*5*|4  |4  ||
||***|7 9|  9||***|7  |***||***|   |   ||
++===+===+===++===+===+===++===+===+===++

Digit 9 appears only once in box 8 in
square 76.  Clear digit 5 from that box
and clear 9 from column 6 and row 7.

++===+===+===++===+===+===++===+===+===++
||1  |1  |***||***|1 3|***||  3|  3|***||
||   |   |*7*||*2*| 5 |*4*||   | 5 |*6*||
||  9| 89|***||***|   |***|| 8 |  9|***||
++---+---+---++---+---+---++---+---+---++
||***|1  |***||***|1 3|  3|| 23| 23|  3||
||*5*|   |*4*||*6*|   |   ||   |   |   ||
||***| 89|***||***|7  |7  ||78 |7 9| 89||
++---+---+---++---+---+---++---+---+---++
|| 23| 23| 2 ||   |***|***||***|   |   ||
||   |  6|  6|| 5 |*9*|*8*||*1*|45 |45 ||
||   |   |   ||7  |***|***||***|7  |   ||
++===+===+===++===+===+===++===+===+===++
||***| 23| 2 ||  3|***|***||  3|  3|  3||
||*6*|45 | 5 || 5 |*8*|*1*||4  | 5 | 5 ||
||***|7 9|  9||7 9|***|***||7  |7 9|  9||
++---+---+---++---+---+---++---+---+---++
|| 23| 23|1  ||  3| 23| 23||   |1 3|  3||
||4  |45 |   || 5 | 5 | 5 ||4 6| 56| 5 ||
||7 9|7 9| 8 ||7 9|7  |7  ||78 |7 9| 89||
++---+---+---++---+---+---++---+---+---++
||  3|  3|1  ||***|***|  3||  3|1 3|***||
||   | 5 |   ||*4*|*6*| 5 ||   | 5 |*2*||
||7 9|7 9| 8 ||***|***|7  ||78 |7 9|***||
++===+===+===++===+===+===++===+===+===++
||1  |1  |***||***|***|***|| 2 | 2 |***||
||   | 5 |*3*||*8*|*4*|*9*||  6|  6|*7*||
||   |   |***||***|***|***||   |   |***||
++---+---+---++---+---+---++---+---+---++
|| 2 | 2 | 2 ||  3| 23| 23||***|***|***||
||4  |456| 56|| 5 | 5 | 5 ||*9*|*8*|*1*||
||7  |7  |   ||7  |7  |7  ||***|***|***||
++---+---+---++---+---+---++---+---+---++
||***| 2 | 2 ||***| 2 |***||***|  3|  3||
||*8*|   |   ||*1*|   |*6*||*5*|4  |4  ||
||***|7 9|  9||***|7  |***||***|   |   ||
++===+===+===++===+===+===++===+===+===++

Naked 1 in square 71.  Clear 1 from row
7 and column 1.

++===+===+===++===+===+===++===+===+===++
||   |1  |***||***|1 3|***||  3|  3|***||
||   |   |*7*||*2*| 5 |*4*||   | 5 |*6*||
||  9| 89|***||***|   |***|| 8 |  9|***||
++---+---+---++---+---+---++---+---+---++
||***|1  |***||***|1 3|  3|| 23| 23|  3||
||*5*|   |*4*||*6*|   |   ||   |   |   ||
||***| 89|***||***|7  |7  ||78 |7 9| 89||
++---+---+---++---+---+---++---+---+---++
|| 23| 23| 2 ||   |***|***||***|   |   ||
||   |  6|  6|| 5 |*9*|*8*||*1*|45 |45 ||
||   |   |   ||7  |***|***||***|7  |   ||
++===+===+===++===+===+===++===+===+===++
||***| 23| 2 ||  3|***|***||  3|  3|  3||
||*6*|45 | 5 || 5 |*8*|*1*||4  | 5 | 5 ||
||***|7 9|  9||7 9|***|***||7  |7 9|  9||
++---+---+---++---+---+---++---+---+---++
|| 23| 23|1  ||  3| 23| 23||   |1 3|  3||
||4  |45 |   || 5 | 5 | 5 ||4 6| 56| 5 ||
||7 9|7 9| 8 ||7 9|7  |7  ||78 |7 9| 89||
++---+---+---++---+---+---++---+---+---++
||  3|  3|1  ||***|***|  3||  3|1 3|***||
||   | 5 |   ||*4*|*6*| 5 ||   | 5 |*2*||
||7 9|7 9| 8 ||***|***|7  ||78 |7 9|***||
++===+===+===++===+===+===++===+===+===++
||***|   |***||***|***|***|| 2 | 2 |***||
||*1*| 5 |*3*||*8*|*4*|*9*||  6|  6|*7*||
||***|   |***||***|***|***||   |   |***||
++---+---+---++---+---+---++---+---+---++
|| 2 | 2 | 2 ||  3| 23| 23||***|***|***||
||4  |456| 56|| 5 | 5 | 5 ||*9*|*8*|*1*||
||7  |7  |   ||7  |7  |7  ||***|***|***||
++---+---+---++---+---+---++---+---+---++
||***| 2 | 2 ||***| 2 |***||***|  3|  3||
||*8*|   |   ||*1*|   |*6*||*5*|4  |4  ||
||***|7 9|  9||***|7  |***||***|   |   ||
++===+===+===++===+===+===++===+===+===++

Naked 9 in square 11 and naked 5 in
square 72.

++===+===+===++===+===+===++===+===+===++
||***|1  |***||***|1 3|***||  3|  3|***||
||*9*|   |*7*||*2*| 5 |*4*||   | 5 |*6*||
||***| 8 |***||***|   |***|| 8 |   |***||
++---+---+---++---+---+---++---+---+---++
||***|1  |***||***|1 3|  3|| 23| 23|  3||
||*5*|   |*4*||*6*|   |   ||   |   |   ||
||***| 8 |***||***|7  |7  ||78 |7 9| 89||
++---+---+---++---+---+---++---+---+---++
|| 23| 23| 2 ||   |***|***||***|   |   ||
||   |  6|  6|| 5 |*9*|*8*||*1*|45 |45 ||
||   |   |   ||7  |***|***||***|7  |   ||
++===+===+===++===+===+===++===+===+===++
||***| 23| 2 ||  3|***|***||  3|  3|  3||
||*6*|4  | 5 || 5 |*8*|*1*||4  | 5 | 5 ||
||***|7 9|  9||7 9|***|***||7  |7 9|  9||
++---+---+---++---+---+---++---+---+---++
|| 23| 23|1  ||  3| 23| 23||   |1 3|  3||
||4  |4  |   || 5 | 5 | 5 ||4 6| 56| 5 ||
||7  |7 9| 8 ||7 9|7  |7  ||78 |7 9| 89||
++---+---+---++---+---+---++---+---+---++
||  3|  3|1  ||***|***|  3||  3|1 3|***||
||   |   |   ||*4*|*6*| 5 ||   | 5 |*2*||
||7  |7 9| 8 ||***|***|7  ||78 |7 9|***||
++===+===+===++===+===+===++===+===+===++
||***|***|***||***|***|***|| 2 | 2 |***||
||*1*|*5*|*3*||*8*|*4*|*9*||  6|  6|*7*||
||***|***|***||***|***|***||   |   |***||
++---+---+---++---+---+---++---+---+---++
|| 2 | 2 | 2 ||  3| 23| 23||***|***|***||
||4  |4 6|  6|| 5 | 5 | 5 ||*9*|*8*|*1*||
||7  |7  |   ||7  |7  |7  ||***|***|***||
++---+---+---++---+---+---++---+---+---++
||***| 2 | 2 ||***| 2 |***||***|  3|  3||
||*8*|   |   ||*1*|   |*6*||*5*|4  |4  ||
||***|7 9|  9||***|7  |***||***|   |   ||
++===+===+===++===+===+===++===+===+===++

Naked pair 2 and 6 in squares 33 and 83
remove other twos from column 3, leaving
naked 9 in square 93, which leaves
a naked 5 in square 43.

++===+===+===++===+===+===++===+===+===++
||***|1  |***||***|1 3|***||  3|  3|***||
||*9*|   |*7*||*2*| 5 |*4*||   | 5 |*6*||
||***| 8 |***||***|   |***|| 8 |   |***||
++---+---+---++---+---+---++---+---+---++
||***|1  |***||***|1 3|  3|| 23| 23|  3||
||*5*|   |*4*||*6*|   |   ||   |   |   ||
||***| 8 |***||***|7  |7  ||78 |7 9| 89||
++---+---+---++---+---+---++---+---+---++
|| 23| 23| 2 ||   |***|***||***|   |   ||
||   |  6|  6|| 5 |*9*|*8*||*1*|45 |45 ||
||   |   |   ||7  |***|***||***|7  |   ||
++===+===+===++===+===+===++===+===+===++
||***| 23|***||  3|***|***||  3|  3|  3||
||*6*|4  |*5*||   |*8*|*1*||4  |   |   ||
||***|7 9|***||7 9|***|***||7  |7 9|  9||
++---+---+---++---+---+---++---+---+---++
|| 23| 23|1  ||  3| 23| 23||   |1 3|  3||
||4  |4  |   || 5 | 5 | 5 ||4 6| 56| 5 ||
||7  |7 9| 8 ||7 9|7  |7  ||78 |7 9| 89||
++---+---+---++---+---+---++---+---+---++
||  3|  3|1  ||***|***|  3||  3|1 3|***||
||   |   |   ||*4*|*6*| 5 ||   | 5 |*2*||
||7  |7 9| 8 ||***|***|7  ||78 |7 9|***||
++===+===+===++===+===+===++===+===+===++
||***|***|***||***|***|***|| 2 | 2 |***||
||*1*|*5*|*3*||*8*|*4*|*9*||  6|  6|*7*||
||***|***|***||***|***|***||   |   |***||
++---+---+---++---+---+---++---+---+---++
|| 2 | 2 | 2 ||  3| 23| 23||***|***|***||
||4  |4 6|  6|| 5 | 5 | 5 ||*9*|*8*|*1*||
||7  |7  |   ||7  |7  |7  ||***|***|***||
++---+---+---++---+---+---++---+---+---++
||***| 2 |***||***| 2 |***||***|  3|  3||
||*8*|   |*9*||*1*|   |*6*||*5*|4  |4  ||
||***|7  |***||***|7  |***||***|   |   ||
++===+===+===++===+===+===++===+===+===++

Row 4 has a digit 2 only in square 42.

++===+===+===++===+===+===++===+===+===++
||***|1  |***||***|1 3|***||  3|  3|***||
||*9*|   |*7*||*2*| 5 |*4*||   | 5 |*6*||
||***| 8 |***||***|   |***|| 8 |   |***||
++---+---+---++---+---+---++---+---+---++
||***|1  |***||***|1 3|  3|| 23| 23|  3||
||*5*|   |*4*||*6*|   |   ||   |   |   ||
||***| 8 |***||***|7  |7  ||78 |7 9| 89||
++---+---+---++---+---+---++---+---+---++
|| 23|  3| 2 ||   |***|***||***|   |   ||
||   |  6|  6|| 5 |*9*|*8*||*1*|45 |45 ||
||   |   |   ||7  |***|***||***|7  |   ||
++===+===+===++===+===+===++===+===+===++
||***|***|***||  3|***|***||  3|  3|  3||
||*6*|*2*|*5*||   |*8*|*1*||4  |   |   ||
||***|***|***||7 9|***|***||7  |7 9|  9||
++---+---+---++---+---+---++---+---+---++
||  3|  3|1  ||  3| 23| 23||   |1 3|  3||
||4  |4  |   || 5 | 5 | 5 ||4 6| 56| 5 ||
||7  |7 9| 8 ||7 9|7  |7  ||78 |7 9| 89||
++---+---+---++---+---+---++---+---+---++
||  3|  3|1  ||***|***|  3||  3|1 3|***||
||   |   |   ||*4*|*6*| 5 ||   | 5 |*2*||
||7  |7 9| 8 ||***|***|7  ||78 |7 9|***||
++===+===+===++===+===+===++===+===+===++
||***|***|***||***|***|***|| 2 | 2 |***||
||*1*|*5*|*3*||*8*|*4*|*9*||  6|  6|*7*||
||***|***|***||***|***|***||   |   |***||
++---+---+---++---+---+---++---+---+---++
|| 2 |   | 2 ||  3| 23| 23||***|***|***||
||4  |4 6|  6|| 5 | 5 | 5 ||*9*|*8*|*1*||
||7  |7  |   ||7  |7  |7  ||***|***|***||
++---+---+---++---+---+---++---+---+---++
||***|   |***||***| 2 |***||***|  3|  3||
||*8*|   |*9*||*1*|   |*6*||*5*|4  |4  ||
||***|7  |***||***|7  |***||***|   |   ||
++===+===+===++===+===+===++===+===+===++

Naked 7 in square 92.

++===+===+===++===+===+===++===+===+===++
||***|1  |***||***|1 3|***||  3|  3|***||
||*9*|   |*7*||*2*| 5 |*4*||   | 5 |*6*||
||***| 8 |***||***|   |***|| 8 |   |***||
++---+---+---++---+---+---++---+---+---++
||***|1  |***||***|1 3|  3|| 23| 23|  3||
||*5*|   |*4*||*6*|   |   ||   |   |   ||
||***| 8 |***||***|7  |7  ||78 |7 9| 89||
++---+---+---++---+---+---++---+---+---++
|| 23|  3| 2 ||   |***|***||***|   |   ||
||   |  6|  6|| 5 |*9*|*8*||*1*|45 |45 ||
||   |   |   ||7  |***|***||***|7  |   ||
++===+===+===++===+===+===++===+===+===++
||***|***|***||  3|***|***||  3|  3|  3||
||*6*|*2*|*5*||   |*8*|*1*||4  |   |   ||
||***|***|***||7 9|***|***||7  |7 9|  9||
++---+---+---++---+---+---++---+---+---++
||  3|  3|1  ||  3| 23| 23||   |1 3|  3||
||4  |4  |   || 5 | 5 | 5 ||4 6| 56| 5 ||
||7  |  9| 8 ||7 9|7  |7  ||78 |7 9| 89||
++---+---+---++---+---+---++---+---+---++
||  3|  3|1  ||***|***|  3||  3|1 3|***||
||   |   |   ||*4*|*6*| 5 ||   | 5 |*2*||
||7  |  9| 8 ||***|***|7  ||78 |7 9|***||
++===+===+===++===+===+===++===+===+===++
||***|***|***||***|***|***|| 2 | 2 |***||
||*1*|*5*|*3*||*8*|*4*|*9*||  6|  6|*7*||
||***|***|***||***|***|***||   |   |***||
++---+---+---++---+---+---++---+---+---++
|| 2 |   | 2 ||  3| 23| 23||***|***|***||
||4  |4 6|  6|| 5 | 5 | 5 ||*9*|*8*|*1*||
||   |   |   ||7  |7  |7  ||***|***|***||
++---+---+---++---+---+---++---+---+---++
||***|***|***||***| 2 |***||***|  3|  3||
||*8*|*7*|*9*||*1*|   |*6*||*5*|4  |4  ||
||***|***|***||***|   |***||***|   |   ||
++===+===+===++===+===+===++===+===+===++

Naked 2 in square 95.

++===+===+===++===+===+===++===+===+===++
||***|1  |***||***|1 3|***||  3|  3|***||
||*9*|   |*7*||*2*| 5 |*4*||   | 5 |*6*||
||***| 8 |***||***|   |***|| 8 |   |***||
++---+---+---++---+---+---++---+---+---++
||***|1  |***||***|1 3|  3|| 23| 23|  3||
||*5*|   |*4*||*6*|   |   ||   |   |   ||
||***| 8 |***||***|7  |7  ||78 |7 9| 89||
++---+---+---++---+---+---++---+---+---++
|| 23|  3| 2 ||   |***|***||***|   |   ||
||   |  6|  6|| 5 |*9*|*8*||*1*|45 |45 ||
||   |   |   ||7  |***|***||***|7  |   ||
++===+===+===++===+===+===++===+===+===++
||***|***|***||  3|***|***||  3|  3|  3||
||*6*|*2*|*5*||   |*8*|*1*||4  |   |   ||
||***|***|***||7 9|***|***||7  |7 9|  9||
++---+---+---++---+---+---++---+---+---++
||  3|  3|1  ||  3|  3| 23||   |1 3|  3||
||4  |4  |   || 5 | 5 | 5 ||4 6| 56| 5 ||
||7  |  9| 8 ||7 9|7  |7  ||78 |7 9| 89||
++---+---+---++---+---+---++---+---+---++
||  3|  3|1  ||***|***|  3||  3|1 3|***||
||   |   |   ||*4*|*6*| 5 ||   | 5 |*2*||
||7  |  9| 8 ||***|***|7  ||78 |7 9|***||
++===+===+===++===+===+===++===+===+===++
||***|***|***||***|***|***|| 2 | 2 |***||
||*1*|*5*|*3*||*8*|*4*|*9*||  6|  6|*7*||
||***|***|***||***|***|***||   |   |***||
++---+---+---++---+---+---++---+---+---++
|| 2 |   | 2 ||  3|  3|  3||***|***|***||
||4  |4 6|  6|| 5 | 5 | 5 ||*9*|*8*|*1*||
||   |   |   ||7  |7  |7  ||***|***|***||
++---+---+---++---+---+---++---+---+---++
||***|***|***||***|***|***||***|  3|  3||
||*8*|*7*|*9*||*1*|*2*|*6*||*5*|4  |4  ||
||***|***|***||***|***|***||***|   |   ||
++===+===+===++===+===+===++===+===+===++

Digit 2 only occurs once in box 5.

++===+===+===++===+===+===++===+===+===++
||***|1  |***||***|1 3|***||  3|  3|***||
||*9*|   |*7*||*2*| 5 |*4*||   | 5 |*6*||
||***| 8 |***||***|   |***|| 8 |   |***||
++---+---+---++---+---+---++---+---+---++
||***|1  |***||***|1 3|  3|| 23| 23|  3||
||*5*|   |*4*||*6*|   |   ||   |   |   ||
||***| 8 |***||***|7  |7  ||78 |7 9| 89||
++---+---+---++---+---+---++---+---+---++
|| 23|  3| 2 ||   |***|***||***|   |   ||
||   |  6|  6|| 5 |*9*|*8*||*1*|45 |45 ||
||   |   |   ||7  |***|***||***|7  |   ||
++===+===+===++===+===+===++===+===+===++
||***|***|***||  3|***|***||  3|  3|  3||
||*6*|*2*|*5*||   |*8*|*1*||4  |   |   ||
||***|***|***||7 9|***|***||7  |7 9|  9||
++---+---+---++---+---+---++---+---+---++
||  3|  3|1  ||  3|  3|***||   |1 3|  3||
||4  |4  |   || 5 | 5 |*2*||4 6| 56| 5 ||
||7  |  9| 8 ||7 9|7  |***||78 |7 9| 89||
++---+---+---++---+---+---++---+---+---++
||  3|  3|1  ||***|***|  3||  3|1 3|***||
||   |   |   ||*4*|*6*| 5 ||   | 5 |*2*||
||7  |  9| 8 ||***|***|7  ||78 |7 9|***||
++===+===+===++===+===+===++===+===+===++
||***|***|***||***|***|***|| 2 | 2 |***||
||*1*|*5*|*3*||*8*|*4*|*9*||  6|  6|*7*||
||***|***|***||***|***|***||   |   |***||
++---+---+---++---+---+---++---+---+---++
|| 2 |   | 2 ||  3|  3|  3||***|***|***||
||4  |4 6|  6|| 5 | 5 | 5 ||*9*|*8*|*1*||
||   |   |   ||7  |7  |7  ||***|***|***||
++---+---+---++---+---+---++---+---+---++
||***|***|***||***|***|***||***|  3|  3||
||*8*|*7*|*9*||*1*|*2*|*6*||*5*|4  |4  ||
||***|***|***||***|***|***||***|   |   ||
++===+===+===++===+===+===++===+===+===++

Digit 4 only occurs in box 4 within row 5,
so digit 4 cannot occur elsewhere in row 5.
This leaves only one digit 4 in box 6.

++===+===+===++===+===+===++===+===+===++
||***|1  |***||***|1 3|***||  3|  3|***||
||*9*|   |*7*||*2*| 5 |*4*||   | 5 |*6*||
||***| 8 |***||***|   |***|| 8 |   |***||
++---+---+---++---+---+---++---+---+---++
||***|1  |***||***|1 3|  3|| 23| 23|  3||
||*5*|   |*4*||*6*|   |   ||   |   |   ||
||***| 8 |***||***|7  |7  ||78 |7 9| 89||
++---+---+---++---+---+---++---+---+---++
|| 23|  3| 2 ||   |***|***||***|   |   ||
||   |  6|  6|| 5 |*9*|*8*||*1*|45 |45 ||
||   |   |   ||7  |***|***||***|7  |   ||
++===+===+===++===+===+===++===+===+===++
||***|***|***||  3|***|***||***|  3|  3||
||*6*|*2*|*5*||   |*8*|*1*||*4*|   |   ||
||***|***|***||7 9|***|***||***|7 9|  9||
++---+---+---++---+---+---++---+---+---++
||  3|  3|1  ||  3|  3|***||   |1 3|  3||
||4  |4  |   || 5 | 5 |*2*||  6| 56| 5 ||
||7  |  9| 8 ||7 9|7  |***||78 |7 9| 89||
++---+---+---++---+---+---++---+---+---++
||  3|  3|1  ||***|***|  3||  3|1 3|***||
||   |   |   ||*4*|*6*| 5 ||   | 5 |*2*||
||7  |  9| 8 ||***|***|7  ||78 |7 9|***||
++===+===+===++===+===+===++===+===+===++
||***|***|***||***|***|***|| 2 | 2 |***||
||*1*|*5*|*3*||*8*|*4*|*9*||  6|  6|*7*||
||***|***|***||***|***|***||   |   |***||
++---+---+---++---+---+---++---+---+---++
|| 2 |   | 2 ||  3|  3|  3||***|***|***||
||4  |4 6|  6|| 5 | 5 | 5 ||*9*|*8*|*1*||
||   |   |   ||7  |7  |7  ||***|***|***||
++---+---+---++---+---+---++---+---+---++
||***|***|***||***|***|***||***|  3|  3||
||*8*|*7*|*9*||*1*|*2*|*6*||*5*|4  |4  ||
||***|***|***||***|***|***||***|   |   ||
++===+===+===++===+===+===++===+===+===++

Digit 7 occurs only twice each in rows 3 and 4,
in the same columns (4 and 8).  Thus,
if digit 7 cannot occur in columns 4 and 8 in
other rows.

++===+===+===++===+===+===++===+===+===++
||***|1  |***||***|1 3|***||  3|  3|***||
||*9*|   |*7*||*2*| 5 |*4*||   | 5 |*6*||
||***| 8 |***||***|   |***|| 8 |   |***||
++---+---+---++---+---+---++---+---+---++
||***|1  |***||***|1 3|  3|| 23| 23|  3||
||*5*|   |*4*||*6*|   |   ||   |   |   ||
||***| 8 |***||***|7  |7  ||78 |  9| 89||
++---+---+---++---+---+---++---+---+---++
|| 23|  3| 2 ||   |***|***||***|   |   ||
||   |  6|  6|| 5 |*9*|*8*||*1*|45 |45 ||
||   |   |   ||7  |***|***||***|7  |   ||
++===+===+===++===+===+===++===+===+===++
||***|***|***||  3|***|***||***|  3|  3||
||*6*|*2*|*5*||   |*8*|*1*||*4*|   |   ||
||***|***|***||7 9|***|***||***|7 9|  9||
++---+---+---++---+---+---++---+---+---++
||  3|  3|1  ||  3|  3|***||   |1 3|  3||
||4  |4  |   || 5 | 5 |*2*||  6| 56| 5 ||
||7  |  9| 8 ||  9|7  |***||78 |  9| 89||
++---+---+---++---+---+---++---+---+---++
||  3|  3|1  ||***|***|  3||  3|1 3|***||
||   |   |   ||*4*|*6*| 5 ||   | 5 |*2*||
||7  |  9| 8 ||***|***|7  ||78 |  9|***||
++===+===+===++===+===+===++===+===+===++
||***|***|***||***|***|***|| 2 | 2 |***||
||*1*|*5*|*3*||*8*|*4*|*9*||  6|  6|*7*||
||***|***|***||***|***|***||   |   |***||
++---+---+---++---+---+---++---+---+---++
|| 2 |   | 2 ||  3|  3|  3||***|***|***||
||4  |4 6|  6|| 5 | 5 | 5 ||*9*|*8*|*1*||
||   |   |   ||   |7  |7  ||***|***|***||
++---+---+---++---+---+---++---+---+---++
||***|***|***||***|***|***||***|  3|  3||
||*8*|*7*|*9*||*1*|*2*|*6*||*5*|4  |4  ||
||***|***|***||***|***|***||***|   |   ||
++===+===+===++===+===+===++===+===+===++

Consider square 18: if it is a 3, then
square 98 is a 4, so square 38 cannot be
a 4.  If square 18 is a 5, then square
39 must be a 4, so again square 38 cannot
be a 4.

++===+===+===++===+===+===++===+===+===++
||***|1  |***||***|1 3|***||  3|  3|***||
||*9*|   |*7*||*2*| 5 |*4*||   | 5 |*6*||
||***| 8 |***||***|   |***|| 8 |   |***||
++---+---+---++---+---+---++---+---+---++
||***|1  |***||***|1 3|  3|| 23| 23|  3||
||*5*|   |*4*||*6*|   |   ||   |   |   ||
||***| 8 |***||***|7  |7  ||78 |  9| 89||
++---+---+---++---+---+---++---+---+---++
|| 23|  3| 2 ||   |***|***||***|   |   ||
||   |  6|  6|| 5 |*9*|*8*||*1*| 5 |45 ||
||   |   |   ||7  |***|***||***|7  |   ||
++===+===+===++===+===+===++===+===+===++
||***|***|***||  3|***|***||***|  3|  3||
||*6*|*2*|*5*||   |*8*|*1*||*4*|   |   ||
||***|***|***||7 9|***|***||***|7 9|  9||
++---+---+---++---+---+---++---+---+---++
||  3|  3|1  ||  3|  3|***||   |1 3|  3||
||4  |4  |   || 5 | 5 |*2*||  6| 56| 5 ||
||7  |  9| 8 ||  9|7  |***||78 |  9| 89||
++---+---+---++---+---+---++---+---+---++
||  3|  3|1  ||***|***|  3||  3|1 3|***||
||   |   |   ||*4*|*6*| 5 ||   | 5 |*2*||
||7  |  9| 8 ||***|***|7  ||78 |  9|***||
++===+===+===++===+===+===++===+===+===++
||***|***|***||***|***|***|| 2 | 2 |***||
||*1*|*5*|*3*||*8*|*4*|*9*||  6|  6|*7*||
||***|***|***||***|***|***||   |   |***||
++---+---+---++---+---+---++---+---+---++
|| 2 |   | 2 ||  3|  3|  3||***|***|***||
||4  |4 6|  6|| 5 | 5 | 5 ||*9*|*8*|*1*||
||   |   |   ||   |7  |7  ||***|***|***||
++---+---+---++---+---+---++---+---+---++
||***|***|***||***|***|***||***|  3|  3||
||*8*|*7*|*9*||*1*|*2*|*6*||*5*|4  |4  ||
||***|***|***||***|***|***||***|   |   ||
++===+===+===++===+===+===++===+===+===++

Naked pair 57 in squares 34 and 38, so
square 39 must be a 4, and square 99
must be a 3, and 98 must be a 4.

++===+===+===++===+===+===++===+===+===++
||***|1  |***||***|1 3|***||  3|  3|***||
||*9*|   |*7*||*2*| 5 |*4*||   | 5 |*6*||
||***| 8 |***||***|   |***|| 8 |   |***||
++---+---+---++---+---+---++---+---+---++
||***|1  |***||***|1 3|  3|| 23| 23|   ||
||*5*|   |*4*||*6*|   |   ||   |   |   ||
||***| 8 |***||***|7  |7  ||78 |  9| 89||
++---+---+---++---+---+---++---+---+---++
|| 23|  3| 2 ||   |***|***||***|   |***||
||   |  6|  6|| 5 |*9*|*8*||*1*| 5 |*4*||
||   |   |   ||7  |***|***||***|7  |***||
++===+===+===++===+===+===++===+===+===++
||***|***|***||  3|***|***||***|  3|   ||
||*6*|*2*|*5*||   |*8*|*1*||*4*|   |   ||
||***|***|***||7 9|***|***||***|7 9|  9||
++---+---+---++---+---+---++---+---+---++
||  3|  3|1  ||  3|  3|***||   |1 3|   ||
||4  |4  |   || 5 | 5 |*2*||  6| 56| 5 ||
||7  |  9| 8 ||  9|7  |***||78 |  9| 89||
++---+---+---++---+---+---++---+---+---++
||  3|  3|1  ||***|***|  3||  3|1 3|***||
||   |   |   ||*4*|*6*| 5 ||   | 5 |*2*||
||7  |  9| 8 ||***|***|7  ||78 |  9|***||
++===+===+===++===+===+===++===+===+===++
||***|***|***||***|***|***|| 2 | 2 |***||
||*1*|*5*|*3*||*8*|*4*|*9*||  6|  6|*7*||
||***|***|***||***|***|***||   |   |***||
++---+---+---++---+---+---++---+---+---++
|| 2 |   | 2 ||  3|  3|  3||***|***|***||
||4  |4 6|  6|| 5 | 5 | 5 ||*9*|*8*|*1*||
||   |   |   ||   |7  |7  ||***|***|***||
++---+---+---++---+---+---++---+---+---++
||***|***|***||***|***|***||***|***|***||
||*8*|*7*|*9*||*1*|*2*|*6*||*5*|*4*|*3*||
||***|***|***||***|***|***||***|***|***||
++===+===+===++===+===+===++===+===+===++

Naked 9 in square 49, so square 29 is 8
and square 59 is 5.

++===+===+===++===+===+===++===+===+===++
||***|1  |***||***|1 3|***||  3|  3|***||
||*9*|   |*7*||*2*| 5 |*4*||   | 5 |*6*||
||***| 8 |***||***|   |***|| 8 |   |***||
++---+---+---++---+---+---++---+---+---++
||***|1  |***||***|1 3|  3|| 23| 23|***||
||*5*|   |*4*||*6*|   |   ||   |   |*8*||
||***|   |***||***|7  |7  ||7  |  9|***||
++---+---+---++---+---+---++---+---+---++
|| 23|  3| 2 ||   |***|***||***|   |***||
||   |  6|  6|| 5 |*9*|*8*||*1*| 5 |*4*||
||   |   |   ||7  |***|***||***|7  |***||
++===+===+===++===+===+===++===+===+===++
||***|***|***||  3|***|***||***|  3|***||
||*6*|*2*|*5*||   |*8*|*1*||*4*|   |*9*||
||***|***|***||7  |***|***||***|7  |***||
++---+---+---++---+---+---++---+---+---++
||  3|  3|1  ||  3|  3|***||   |1 3|***||
||4  |4  |   ||   |   |*2*||  6|  6|*5*||
||7  |  9| 8 ||  9|7  |***||78 |   |***||
++---+---+---++---+---+---++---+---+---++
||  3|  3|1  ||***|***|  3||  3|1 3|***||
||   |   |   ||*4*|*6*| 5 ||   |   |*2*||
||7  |  9| 8 ||***|***|7  ||78 |   |***||
++===+===+===++===+===+===++===+===+===++
||***|***|***||***|***|***|| 2 | 2 |***||
||*1*|*5*|*3*||*8*|*4*|*9*||  6|  6|*7*||
||***|***|***||***|***|***||   |   |***||
++---+---+---++---+---+---++---+---+---++
|| 2 |   | 2 ||  3|  3|  3||***|***|***||
||4  |4 6|  6|| 5 | 5 | 5 ||*9*|*8*|*1*||
||   |   |   ||   |7  |7  ||***|***|***||
++---+---+---++---+---+---++---+---+---++
||***|***|***||***|***|***||***|***|***||
||*8*|*7*|*9*||*1*|*2*|*6*||*5*|*4*|*3*||
||***|***|***||***|***|***||***|***|***||
++===+===+===++===+===+===++===+===+===++

Naked 1 in square 22 and hidden 9 in
column 4 (square 54)

++===+===+===++===+===+===++===+===+===++
||***|   |***||***|1 3|***||  3|  3|***||
||*9*|   |*7*||*2*| 5 |*4*||   | 5 |*6*||
||***| 8 |***||***|   |***|| 8 |   |***||
++---+---+---++---+---+---++---+---+---++
||***|***|***||***|  3|  3|| 23| 23|***||
||*5*|*1*|*4*||*6*|   |   ||   |   |*8*||
||***|***|***||***|7  |7  ||7  |  9|***||
++---+---+---++---+---+---++---+---+---++
|| 23|  3| 2 ||   |***|***||***|   |***||
||   |  6|  6|| 5 |*9*|*8*||*1*| 5 |*4*||
||   |   |   ||7  |***|***||***|7  |***||
++===+===+===++===+===+===++===+===+===++
||***|***|***||  3|***|***||***|  3|***||
||*6*|*2*|*5*||   |*8*|*1*||*4*|   |*9*||
||***|***|***||7  |***|***||***|7  |***||
++---+---+---++---+---+---++---+---+---++
||  3|  3|1  ||***|  3|***||   |1 3|***||
||4  |4  |   ||*9*|   |*2*||  6|  6|*5*||
||7  |   | 8 ||***|7  |***||78 |   |***||
++---+---+---++---+---+---++---+---+---++
||  3|  3|1  ||***|***|  3||  3|1 3|***||
||   |   |   ||*4*|*6*| 5 ||   |   |*2*||
||7  |  9| 8 ||***|***|7  ||78 |   |***||
++===+===+===++===+===+===++===+===+===++
||***|***|***||***|***|***|| 2 | 2 |***||
||*1*|*5*|*3*||*8*|*4*|*9*||  6|  6|*7*||
||***|***|***||***|***|***||   |   |***||
++---+---+---++---+---+---++---+---+---++
|| 2 |   | 2 ||  3|  3|  3||***|***|***||
||4  |4 6|  6|| 5 | 5 | 5 ||*9*|*8*|*1*||
||   |   |   ||   |7  |7  ||***|***|***||
++---+---+---++---+---+---++---+---+---++
||***|***|***||***|***|***||***|***|***||
||*8*|*7*|*9*||*1*|*2*|*6*||*5*|*4*|*3*||
||***|***|***||***|***|***||***|***|***||
++===+===+===++===+===+===++===+===+===++

Naked pair in squares 44 and 55 means
square 66 is 5, and naked pair in squares
25 and 26 means square 27 is 2, and
naked 8 in square 12 means square 17
is a 3.

++===+===+===++===+===+===++===+===+===++
||***|***|***||***|1  |***||***|***|***||
||*9*|*8*|*7*||*2*|   |*4*||*3*|*5*|*6*||
||***|***|***||***|   |***||***|***|***||
++---+---+---++---+---+---++---+---+---++
||***|***|***||***|  3|  3||***|   |***||
||*5*|*1*|*4*||*6*|   |   ||*2*|   |*8*||
||***|***|***||***|7  |7  ||***|  9|***||
++---+---+---++---+---+---++---+---+---++
|| 23|  3| 2 ||   |***|***||***|   |***||
||   |  6|  6|| 5 |*9*|*8*||*1*|   |*4*||
||   |   |   ||7  |***|***||***|7  |***||
++===+===+===++===+===+===++===+===+===++
||***|***|***||  3|***|***||***|  3|***||
||*6*|*2*|*5*||   |*8*|*1*||*4*|   |*9*||
||***|***|***||7  |***|***||***|7  |***||
++---+---+---++---+---+---++---+---+---++
||  3|  3|1  ||***|  3|***||   |1 3|***||
||4  |4  |   ||*9*|   |*2*||   |  6|*5*||
||7  |   | 8 ||***|7  |***||78 |   |***||
++---+---+---++---+---+---++---+---+---++
||  3|  3|1  ||***|***|***||   |1 3|***||
||   |   |   ||*4*|*6*|*5*||   |   |*2*||
||7  |  9| 8 ||***|***|***||78 |   |***||
++===+===+===++===+===+===++===+===+===++
||***|***|***||***|***|***||***| 2 |***||
||*1*|*5*|*3*||*8*|*4*|*9*||*6*|   |*7*||
||***|***|***||***|***|***||***|   |***||
++---+---+---++---+---+---++---+---+---++
|| 2 |   | 2 ||  3|  3|  3||***|***|***||
||4  |4 6|  6|| 5 | 5 |   ||*9*|*8*|*1*||
||   |   |   ||   |7  |7  ||***|***|***||
++---+---+---++---+---+---++---+---+---++
||***|***|***||***|***|***||***|***|***||
||*8*|*7*|*9*||*1*|*2*|*6*||*5*|*4*|*3*||
||***|***|***||***|***|***||***|***|***||
++===+===+===++===+===+===++===+===+===++

Naked 5 in square 18 and naked 6 in
square 77 and naked 9 in square 28 and
naked 7 in square 38.

++===+===+===++===+===+===++===+===+===++
||***|***|***||***|***|***||***|***|***||
||*9*|*8*|*7*||*2*|*1*|*4*||*3*|*5*|*6*||
||***|***|***||***|***|***||***|***|***||
++---+---+---++---+---+---++---+---+---++
||***|***|***||***|  3|  3||***|***|***||
||*5*|*1*|*4*||*6*|   |   ||*2*|*9*|*8*||
||***|***|***||***|7  |7  ||***|***|***||
++---+---+---++---+---+---++---+---+---++
|| 23|  3| 2 ||   |***|***||***|***|***||
||   |  6|  6|| 5 |*9*|*8*||*1*|*7*|*4*||
||   |   |   ||   |***|***||***|***|***||
++===+===+===++===+===+===++===+===+===++
||***|***|***||  3|***|***||***|  3|***||
||*6*|*2*|*5*||   |*8*|*1*||*4*|   |*9*||
||***|***|***||7  |***|***||***|   |***||
++---+---+---++---+---+---++---+---+---++
||  3|  3|1  ||***|  3|***||   |1 3|***||
||4  |4  |   ||*9*|   |*2*||   |  6|*5*||
||7  |   | 8 ||***|7  |***||78 |   |***||
++---+---+---++---+---+---++---+---+---++
||  3|  3|1  ||***|***|***||   |1 3|***||
||   |   |   ||*4*|*6*|*5*||   |   |*2*||
||7  |  9| 8 ||***|***|***||78 |   |***||
++===+===+===++===+===+===++===+===+===++
||***|***|***||***|***|***||***| 2 |***||
||*1*|*5*|*3*||*8*|*4*|*9*||*6*|   |*7*||
||***|***|***||***|***|***||***|   |***||
++---+---+---++---+---+---++---+---+---++
|| 2 |   | 2 ||  3|  3|  3||***|***|***||
||4  |4 6|  6|| 5 | 5 |   ||*9*|*8*|*1*||
||   |   |   ||   |7  |7  ||***|***|***||
++---+---+---++---+---+---++---+---+---++
||***|***|***||***|***|***||***|***|***||
||*8*|*7*|*9*||*1*|*2*|*6*||*5*|*4*|*3*||
||***|***|***||***|***|***||***|***|***||
++===+===+===++===+===+===++===+===+===++

Naked 3 in square 48 and naked 2 in
square 87 and naked 5 in square 34.

++===+===+===++===+===+===++===+===+===++
||***|***|***||***|***|***||***|***|***||
||*9*|*8*|*7*||*2*|*1*|*4*||*3*|*5*|*6*||
||***|***|***||***|***|***||***|***|***||
++---+---+---++---+---+---++---+---+---++
||***|***|***||***|  3|  3||***|***|***||
||*5*|*1*|*4*||*6*|   |   ||*2*|*9*|*8*||
||***|***|***||***|7  |7  ||***|***|***||
++---+---+---++---+---+---++---+---+---++
|| 23|  3| 2 ||***|***|***||***|***|***||
||   |  6|  6||*5*|*9*|*8*||*1*|*7*|*4*||
||   |   |   ||***|***|***||***|***|***||
++===+===+===++===+===+===++===+===+===++
||***|***|***||  3|***|***||***|***|***||
||*6*|*2*|*5*||   |*8*|*1*||*4*|*3*|*9*||
||***|***|***||7  |***|***||***|***|***||
++---+---+---++---+---+---++---+---+---++
||  3|  3|1  ||***|  3|***||   |1  |***||
||4  |4  |   ||*9*|   |*2*||   |  6|*5*||
||7  |   | 8 ||***|7  |***||78 |   |***||
++---+---+---++---+---+---++---+---+---++
||  3|  3|1  ||***|***|***||   |1  |***||
||   |   |   ||*4*|*6*|*5*||   |   |*2*||
||7  |  9| 8 ||***|***|***||78 |   |***||
++===+===+===++===+===+===++===+===+===++
||***|***|***||***|***|***||***|***|***||
||*1*|*5*|*3*||*8*|*4*|*9*||*6*|*2*|*7*||
||***|***|***||***|***|***||***|***|***||
++---+---+---++---+---+---++---+---+---++
|| 2 |   | 2 ||  3|  3|  3||***|***|***||
||4  |4 6|  6||   | 5 |   ||*9*|*8*|*1*||
||   |   |   ||   |7  |7  ||***|***|***||
++---+---+---++---+---+---++---+---+---++
||***|***|***||***|***|***||***|***|***||
||*8*|*7*|*9*||*1*|*2*|*6*||*5*|*4*|*3*||
||***|***|***||***|***|***||***|***|***||
++===+===+===++===+===+===++===+===+===++

Hidden 9 in box 4 and naked 1 in square 68
and naked 3 in square 84.

++===+===+===++===+===+===++===+===+===++
||***|***|***||***|***|***||***|***|***||
||*9*|*8*|*7*||*2*|*1*|*4*||*3*|*5*|*6*||
||***|***|***||***|***|***||***|***|***||
++---+---+---++---+---+---++---+---+---++
||***|***|***||***|  3|  3||***|***|***||
||*5*|*1*|*4*||*6*|   |   ||*2*|*9*|*8*||
||***|***|***||***|7  |7  ||***|***|***||
++---+---+---++---+---+---++---+---+---++
|| 23|  3| 2 ||***|***|***||***|***|***||
||   |  6|  6||*5*|*9*|*8*||*1*|*7*|*4*||
||   |   |   ||***|***|***||***|***|***||
++===+===+===++===+===+===++===+===+===++
||***|***|***||  3|***|***||***|***|***||
||*6*|*2*|*5*||   |*8*|*1*||*4*|*3*|*9*||
||***|***|***||7  |***|***||***|***|***||
++---+---+---++---+---+---++---+---+---++
||  3|  3|1  ||***|  3|***||   |   |***||
||4  |4  |   ||*9*|   |*2*||   |  6|*5*||
||7  |   | 8 ||***|7  |***||78 |   |***||
++---+---+---++---+---+---++---+---+---++
||  3|***|   ||***|***|***||   |***|***||
||   |*9*|   ||*4*|*6*|*5*||   |*1*|*2*||
||7  |***| 8 ||***|***|***||78 |***|***||
++===+===+===++===+===+===++===+===+===++
||***|***|***||***|***|***||***|***|***||
||*1*|*5*|*3*||*8*|*4*|*9*||*6*|*2*|*7*||
||***|***|***||***|***|***||***|***|***||
++---+---+---++---+---+---++---+---+---++
|| 2 |   | 2 ||***|   |   ||***|***|***||
||4  |4 6|  6||*3*| 5 |   ||*9*|*8*|*1*||
||   |   |   ||***|7  |7  ||***|***|***||
++---+---+---++---+---+---++---+---+---++
||***|***|***||***|***|***||***|***|***||
||*8*|*7*|*9*||*1*|*2*|*6*||*5*|*4*|*3*||
||***|***|***||***|***|***||***|***|***||
++===+===+===++===+===+===++===+===+===++

Naked 7 in square 86 and naked 6 in
square 58 and naked 8 in square 63.

++===+===+===++===+===+===++===+===+===++
||***|***|***||***|***|***||***|***|***||
||*9*|*8*|*7*||*2*|*1*|*4*||*3*|*5*|*6*||
||***|***|***||***|***|***||***|***|***||
++---+---+---++---+---+---++---+---+---++
||***|***|***||***|  3|  3||***|***|***||
||*5*|*1*|*4*||*6*|   |   ||*2*|*9*|*8*||
||***|***|***||***|7  |   ||***|***|***||
++---+---+---++---+---+---++---+---+---++
|| 23|  3| 2 ||***|***|***||***|***|***||
||   |  6|  6||*5*|*9*|*8*||*1*|*7*|*4*||
||   |   |   ||***|***|***||***|***|***||
++===+===+===++===+===+===++===+===+===++
||***|***|***||  3|***|***||***|***|***||
||*6*|*2*|*5*||   |*8*|*1*||*4*|*3*|*9*||
||***|***|***||7  |***|***||***|***|***||
++---+---+---++---+---+---++---+---+---++
||  3|  3|1  ||***|  3|***||   |***|***||
||4  |4  |   ||*9*|   |*2*||   |*6*|*5*||
||7  |   | 8 ||***|7  |***||78 |***|***||
++---+---+---++---+---+---++---+---+---++
||  3|***|***||***|***|***||   |***|***||
||   |*9*|*8*||*4*|*6*|*5*||   |*1*|*2*||
||7  |***|***||***|***|***||7  |***|***||
++===+===+===++===+===+===++===+===+===++
||***|***|***||***|***|***||***|***|***||
||*1*|*5*|*3*||*8*|*4*|*9*||*6*|*2*|*7*||
||***|***|***||***|***|***||***|***|***||
++---+---+---++---+---+---++---+---+---++
|| 2 |   | 2 ||***|   |***||***|***|***||
||4  |4 6|  6||*3*| 5 |*7*||*9*|*8*|*1*||
||   |   |   ||***|   |***||***|***|***||
++---+---+---++---+---+---++---+---+---++
||***|***|***||***|***|***||***|***|***||
||*8*|*7*|*9*||*1*|*2*|*6*||*5*|*4*|*3*||
||***|***|***||***|***|***||***|***|***||
++===+===+===++===+===+===++===+===+===++

Naked 5 in square 85, naked 7 in square 67,
and naked 3 in square 26.

++===+===+===++===+===+===++===+===+===++
||***|***|***||***|***|***||***|***|***||
||*9*|*8*|*7*||*2*|*1*|*4*||*3*|*5*|*6*||
||***|***|***||***|***|***||***|***|***||
++---+---+---++---+---+---++---+---+---++
||***|***|***||***|   |***||***|***|***||
||*5*|*1*|*4*||*6*|   |*3*||*2*|*9*|*8*||
||***|***|***||***|7  |***||***|***|***||
++---+---+---++---+---+---++---+---+---++
|| 23|  3| 2 ||***|***|***||***|***|***||
||   |  6|  6||*5*|*9*|*8*||*1*|*7*|*4*||
||   |   |   ||***|***|***||***|***|***||
++===+===+===++===+===+===++===+===+===++
||***|***|***||  3|***|***||***|***|***||
||*6*|*2*|*5*||   |*8*|*1*||*4*|*3*|*9*||
||***|***|***||7  |***|***||***|***|***||
++---+---+---++---+---+---++---+---+---++
||  3|  3|1  ||***|  3|***||   |***|***||
||4  |4  |   ||*9*|   |*2*||   |*6*|*5*||
||7  |   | 8 ||***|7  |***|| 8 |***|***||
++---+---+---++---+---+---++---+---+---++
||  3|***|***||***|***|***||***|***|***||
||   |*9*|*8*||*4*|*6*|*5*||*7*|*1*|*2*||
||   |***|***||***|***|***||***|***|***||
++===+===+===++===+===+===++===+===+===++
||***|***|***||***|***|***||***|***|***||
||*1*|*5*|*3*||*8*|*4*|*9*||*6*|*2*|*7*||
||***|***|***||***|***|***||***|***|***||
++---+---+---++---+---+---++---+---+---++
|| 2 |   | 2 ||***|***|***||***|***|***||
||4  |4 6|  6||*3*|*5*|*7*||*9*|*8*|*1*||
||   |   |   ||***|***|***||***|***|***||
++---+---+---++---+---+---++---+---+---++
||***|***|***||***|***|***||***|***|***||
||*8*|*7*|*9*||*1*|*2*|*6*||*5*|*4*|*3*||
||***|***|***||***|***|***||***|***|***||
++===+===+===++===+===+===++===+===+===++

Naked 3 in square 61, naked 8 in square 57,
and naked 7 in square 25.

++===+===+===++===+===+===++===+===+===++
||***|***|***||***|***|***||***|***|***||
||*9*|*8*|*7*||*2*|*1*|*4*||*3*|*5*|*6*||
||***|***|***||***|***|***||***|***|***||
++---+---+---++---+---+---++---+---+---++
||***|***|***||***|***|***||***|***|***||
||*5*|*1*|*4*||*6*|*7*|*3*||*2*|*9*|*8*||
||***|***|***||***|***|***||***|***|***||
++---+---+---++---+---+---++---+---+---++
|| 2 |  3| 2 ||***|***|***||***|***|***||
||   |  6|  6||*5*|*9*|*8*||*1*|*7*|*4*||
||   |   |   ||***|***|***||***|***|***||
++===+===+===++===+===+===++===+===+===++
||***|***|***||  3|***|***||***|***|***||
||*6*|*2*|*5*||   |*8*|*1*||*4*|*3*|*9*||
||***|***|***||7  |***|***||***|***|***||
++---+---+---++---+---+---++---+---+---++
||   |  3|1  ||***|  3|***||***|***|***||
||4  |4  |   ||*9*|   |*2*||*8*|*6*|*5*||
||7  |   |   ||***|   |***||***|***|***||
++---+---+---++---+---+---++---+---+---++
||***|***|***||***|***|***||***|***|***||
||*3*|*9*|*8*||*4*|*6*|*5*||*7*|*1*|*2*||
||***|***|***||***|***|***||***|***|***||
++===+===+===++===+===+===++===+===+===++
||***|***|***||***|***|***||***|***|***||
||*1*|*5*|*3*||*8*|*4*|*9*||*6*|*2*|*7*||
||***|***|***||***|***|***||***|***|***||
++---+---+---++---+---+---++---+---+---++
|| 2 |   | 2 ||***|***|***||***|***|***||
||4  |4 6|  6||*3*|*5*|*7*||*9*|*8*|*1*||
||   |   |   ||***|***|***||***|***|***||
++---+---+---++---+---+---++---+---+---++
||***|***|***||***|***|***||***|***|***||
||*8*|*7*|*9*||*1*|*2*|*6*||*5*|*4*|*3*||
||***|***|***||***|***|***||***|***|***||
++===+===+===++===+===+===++===+===+===++

Naked 2 in square 31, naked 1 in square 43,
and naked 3 in square 45.

++===+===+===++===+===+===++===+===+===++
||***|***|***||***|***|***||***|***|***||
||*9*|*8*|*7*||*2*|*1*|*4*||*3*|*5*|*6*||
||***|***|***||***|***|***||***|***|***||
++---+---+---++---+---+---++---+---+---++
||***|***|***||***|***|***||***|***|***||
||*5*|*1*|*4*||*6*|*7*|*3*||*2*|*9*|*8*||
||***|***|***||***|***|***||***|***|***||
++---+---+---++---+---+---++---+---+---++
||***|  3|   ||***|***|***||***|***|***||
||*2*|  6|  6||*5*|*9*|*8*||*1*|*7*|*4*||
||***|   |   ||***|***|***||***|***|***||
++===+===+===++===+===+===++===+===+===++
||***|***|***||   |***|***||***|***|***||
||*6*|*2*|*5*||   |*8*|*1*||*4*|*3*|*9*||
||***|***|***||7  |***|***||***|***|***||
++---+---+---++---+---+---++---+---+---++
||   |   |***||***|***|***||***|***|***||
||4  |4  |*1*||*9*|*3*|*2*||*8*|*6*|*5*||
||7  |   |***||***|***|***||***|***|***||
++---+---+---++---+---+---++---+---+---++
||***|***|***||***|***|***||***|***|***||
||*3*|*9*|*8*||*4*|*6*|*5*||*7*|*1*|*2*||
||***|***|***||***|***|***||***|***|***||
++===+===+===++===+===+===++===+===+===++
||***|***|***||***|***|***||***|***|***||
||*1*|*5*|*3*||*8*|*4*|*9*||*6*|*2*|*7*||
||***|***|***||***|***|***||***|***|***||
++---+---+---++---+---+---++---+---+---++
||   |   | 2 ||***|***|***||***|***|***||
||4  |4 6|  6||*3*|*5*|*7*||*9*|*8*|*1*||
||   |   |   ||***|***|***||***|***|***||
++---+---+---++---+---+---++---+---+---++
||***|***|***||***|***|***||***|***|***||
||*8*|*7*|*9*||*1*|*2*|*6*||*5*|*4*|*3*||
||***|***|***||***|***|***||***|***|***||
++===+===+===++===+===+===++===+===+===++

Naked 7 in square 44, naked 4 in square 52,
naked 6 in square 33, and naked 4 in
square 81.

++===+===+===++===+===+===++===+===+===++
||***|***|***||***|***|***||***|***|***||
||*9*|*8*|*7*||*2*|*1*|*4*||*3*|*5*|*6*||
||***|***|***||***|***|***||***|***|***||
++---+---+---++---+---+---++---+---+---++
||***|***|***||***|***|***||***|***|***||
||*5*|*1*|*4*||*6*|*7*|*3*||*2*|*9*|*8*||
||***|***|***||***|***|***||***|***|***||
++---+---+---++---+---+---++---+---+---++
||***|  3|***||***|***|***||***|***|***||
||*2*|   |*6*||*5*|*9*|*8*||*1*|*7*|*4*||
||***|   |***||***|***|***||***|***|***||
++===+===+===++===+===+===++===+===+===++
||***|***|***||***|***|***||***|***|***||
||*6*|*2*|*5*||*7*|*8*|*1*||*4*|*3*|*9*||
||***|***|***||***|***|***||***|***|***||
++---+---+---++---+---+---++---+---+---++
||   |***|***||***|***|***||***|***|***||
||   |*4*|*1*||*9*|*3*|*2*||*8*|*6*|*5*||
||7  |***|***||***|***|***||***|***|***||
++---+---+---++---+---+---++---+---+---++
||***|***|***||***|***|***||***|***|***||
||*3*|*9*|*8*||*4*|*6*|*5*||*7*|*1*|*2*||
||***|***|***||***|***|***||***|***|***||
++===+===+===++===+===+===++===+===+===++
||***|***|***||***|***|***||***|***|***||
||*1*|*5*|*3*||*8*|*4*|*9*||*6*|*2*|*7*||
||***|***|***||***|***|***||***|***|***||
++---+---+---++---+---+---++---+---+---++
||***|   | 2 ||***|***|***||***|***|***||
||*4*|  6|   ||*3*|*5*|*7*||*9*|*8*|*1*||
||***|   |   ||***|***|***||***|***|***||
++---+---+---++---+---+---++---+---+---++
||***|***|***||***|***|***||***|***|***||
||*8*|*7*|*9*||*1*|*2*|*6*||*5*|*4*|*3*||
||***|***|***||***|***|***||***|***|***||
++===+===+===++===+===+===++===+===+===++

Done!

++===+===+===++===+===+===++===+===+===++
||***|***|***||***|***|***||***|***|***||
||*9*|*8*|*7*||*2*|*1*|*4*||*3*|*5*|*6*||
||***|***|***||***|***|***||***|***|***||
++---+---+---++---+---+---++---+---+---++
||***|***|***||***|***|***||***|***|***||
||*5*|*1*|*4*||*6*|*7*|*3*||*2*|*9*|*8*||
||***|***|***||***|***|***||***|***|***||
++---+---+---++---+---+---++---+---+---++
||***|***|***||***|***|***||***|***|***||
||*2*|*3*|*6*||*5*|*9*|*8*||*1*|*7*|*4*||
||***|***|***||***|***|***||***|***|***||
++===+===+===++===+===+===++===+===+===++
||***|***|***||***|***|***||***|***|***||
||*6*|*2*|*5*||*7*|*8*|*1*||*4*|*3*|*9*||
||***|***|***||***|***|***||***|***|***||
++---+---+---++---+---+---++---+---+---++
||***|***|***||***|***|***||***|***|***||
||*7*|*4*|*1*||*9*|*3*|*2*||*8*|*6*|*5*||
||***|***|***||***|***|***||***|***|***||
++---+---+---++---+---+---++---+---+---++
||***|***|***||***|***|***||***|***|***||
||*3*|*9*|*8*||*4*|*6*|*5*||*7*|*1*|*2*||
||***|***|***||***|***|***||***|***|***||
++===+===+===++===+===+===++===+===+===++
||***|***|***||***|***|***||***|***|***||
||*1*|*5*|*3*||*8*|*4*|*9*||*6*|*2*|*7*||
||***|***|***||***|***|***||***|***|***||
++---+---+---++---+---+---++---+---+---++
||***|***|***||***|***|***||***|***|***||
||*4*|*6*|*2*||*3*|*5*|*7*||*9*|*8*|*1*||
||***|***|***||***|***|***||***|***|***||
++---+---+---++---+---+---++---+---+---++
||***|***|***||***|***|***||***|***|***||
||*8*|*7*|*9*||*1*|*2*|*6*||*5*|*4*|*3*||
||***|***|***||***|***|***||***|***|***||
++===+===+===++===+===+===++===+===+===++