Sudoku Puzzle © Kevin Stone

R1C1 can only be <7>

R2C8 can only be <4>

R5C5 can only be <6>

R7C3 can only be <2>

R2C2 can only be <2>

R3C7 can only be <1>

R7C7 can only be <5>

R1C9 can only be <6>

R1C5 can only be <4>

R3C3 can only be <4>

R7C5 can only be <9>

R4C7 can only be <4>

R2C4 can only be <9>

R5C2 is the only square in row 5 that can be <4>

R5C9 is the only square in row 5 that can be <8>

R4C2 is the only square in row 4 that can be <8>

R9C4 is the only square in row 9 that can be <4>

Squares R2C5 and R9C5 in column 5 form a simple locked pair. These 2 squares both contain the 2 possibilities <58>. Since each of the squares must contain one of the possibilities, they can be eliminated from the other squares in the column.

R8C5 - removing <5> from <257> leaving <27>

Squares R5C8 and R8C8 in column 8 form a simple locked pair. These 2 squares both contain the 2 possibilities <13>. Since each of the squares must contain one of the possibilities, they can be eliminated from the other squares in the column.

R4C8 - removing <3> from <356> leaving <56>

R6C8 - removing <1> from <156> leaving <56>

Squares R7C4 and R7C6 in block 8 form a simple locked pair. These 2 squares both contain the 2 possibilities <16>. Since each of the squares must contain one of the possibilities, they can be eliminated from the other squares in the block.

R8C4 - removing <1> from <123> leaving <23>

R8C6 - removing <1> from <1357> leaving <357>

R9C6 - removing <1> from <1358> leaving <358>

Squares R2C5, R2C6, R9C5 and R9C6 form a Type-1 Unique Rectangle on <58>.

R9C6 - removing <58> from <358> leaving <3>

R9C9 can only be <1>

R1C6 can only be <1>

R8C4 can only be <2>

R9C1 can only be <5>

R6C9 can only be <2>

R8C8 can only be <3>

R1C4 can only be <3>

R7C6 can only be <6>

R4C9 can only be <3>

R7C4 can only be <1>

R3C6 can only be <7>

R8C5 can only be <7>

R3C4 can only be <6>

R8C6 can only be <5>

R3C5 can only be <2>

R8C2 can only be <1>

R2C6 can only be <8>

R9C5 can only be <8>

R5C8 can only be <1>

R4C1 can only be <2>

R2C5 can only be <5>

R4C3 can only be <6>

R5C1 can only be <9>

R6C2 can only be <5>

R4C8 can only be <5>

R6C3 can only be <7>

R6C8 can only be <6>

R5C7 can only be <7>

R6C1 can only be <1>

R5C3 can only be <3>

R6C7 can only be <9>