https://www.abebooks.com/9781250896025/Will-Shortz-Presents-Hard-Sudoku-1250896029/plp
Will Shortz Presents Hard Sudoku, Volume 7 - Shortz, Will: 9781250896025 - AbeBooks
The next in our series of only the toughest puzzles for serious sudoku solvers! Do you have what it takes? These 200 challenging sudoku puzzles from Will...
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