Sudoku Puzzle © Kevin Stone

R2C7 is the only square in row 2 that can be <7>

R4C5 is the only square in row 4 that can be <7>

R5C5 is the only square in row 5 that can be <3>

R5C6 is the only square in row 5 that can be <4>

R5C7 is the only square in row 5 that can be <9>

R8C7 can only be <2>

R9C7 can only be <1>

R9C9 can only be <8>

R1C7 can only be <6>

R7C9 can only be <4>

R7C8 can only be <9>

R7C5 can only be <6>

R8C8 can only be <3>

R7C1 can only be <8>

R7C2 can only be <7>

R1C5 is the only square in row 1 that can be <4>

R3C5 can only be <2>

R3C9 can only be <1>

R3C1 can only be <6>

R1C9 can only be <2>

R1C1 can only be <1>

R1C3 can only be <8>

R5C9 can only be <6>

R2C8 can only be <4>

R3C8 can only be <8>

R3C2 can only be <4>

R5C4 is the only square in row 5 that can be <1>

R2C4 can only be <6>

R2C6 can only be <1>

R8C3 is the only square in column 3 that can be <6>

R8C2 can only be <5>

R8C4 can only be <8>

R2C2 can only be <2>

R9C1 can only be <2>

R8C6 can only be <9>

R4C4 can only be <2>

R6C6 can only be <6>

R9C5 can only be <5>

R9C3 can only be <9>

R5C1 can only be <5>

R6C5 can only be <9>

R2C3 can only be <5>

R5C3 can only be <2>

R4C8 can only be <1>

R6C4 can only be <5>

R4C2 can only be <6>

R6C8 can only be <2>

R6C2 can only be <1>

R4C6 can only be <8>