Jigsaw Sudoku: 400 Hard to Very Sudoku Puzzles: 24 (Irregularly Shaped Sudoku)

Jigsaw Sudoku: 400 Medium to Hard Sudoku Puzzles: 23 (Irregularly Shaped Sudoku)

Jigsaw Sudoku: 250 Medium to Hard Sudoku Puzzles: 15 (Irregularly Shaped Sudoku)

Jigsaw Sudoku: 500 Very Hard Irregular Sudoku Puzzles

400 Killer Sudoku: Hard to Very Sudoku Puzzles: Volume 16 (Sudoku Killer)