Sudoku: 600 Sudoku Puzzles Plus Techniques and Solutions (Easy Sudoku, Medium Sudoku, Hard Sudoku, Very Hard Sudoku) (Volume 1): Montes, William: 9781547019540: Amazon.com: Books
1010 SUDOKU PUZZLES FOR ADULTS: Sudoku Book - Lots Of Fun Sudoku: Beginner - Medium - Hard (Easy to Hard): Grindle, Michael: 9798727060452: Amazon.com: Books