Killer Sudoku Puzzles Hard for Adults Large Print: Sum Sudoku Puzzle Book with 600 Puzzles for Advanced and Professionals (Sumdoku Puzzle Book): Books & Publishing, Flatline: 9798413587829: Amazon.com: Books
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Sum Sudoku: Play Sum Sudoku and Calculate your IQ (Best Brain Games Series): Bayeh, Claude Ziad: 9781517226053: Amazon.com: Books
Hard Killer Sudoku: 250 Sum Sudoku Puzzles for Adults (Paperback) | Harvard Book Store