Will Shortz Presents The Huge Book of Hard Sudoku: 300 Challenging Puzzles
Sudoku 3: 200 Puzzles: Hard to Extreme
Will Shortz Presents Surrender to Sudoku: 200 Irresistibly Hard Puzzles
Beyond Black Belt Sudoku: If you have to ask, it's too hard for you. (Martial Arts Puzzles Series)
Will Shortz Presents Ferocious Sudoku: 200 Hard Puzzles
Hard Sudoku Book: 200 Difficult Sudoku Puzzles (Volume 1)
Will Shortz Presents Genius Sudoku: 200 Extreme Puzzles
Will Shortz Presents Survival of the Fittest Sudoku: 200 Hard Puzzles
Sudoku 3: Extreme to Grand Master