Sudoku For Puzzle Lovers: Very Hard Puzzles, Volume 3: 1000+ Sudoku Puzzles of Tough Challenge for Adults, Seniors, Kids, and Children who Love Number Games and Brain Teasers
Pocket Sudoku for Puzzle Lovers: Easy Puzzles, Volume 5: 200+ Pocket-Sized Travel Sudoku Puzzles of Easy to Medium Challenge for Adults, Seniors, ... who Love Number Games and Brain Teasers