Killer-Sudoku 7 - ultrahardcore

That's the hardest thing to do? Yes, it does! Already in volumes 27 and 32 Stefan Heine, team captain of the two-time Sudoku world champion Germany, believed to have developed the most difficult possible killer Sudokus ever. In international comparison this was also true: Heine's puzzles are by far the most difficult in the world. With this book, however, the bar is raised considerably higher. Killer-Sudoku ultrahardcore - puzzles where even the author takes forever for each of these 500 masterpieces!