500 sudoku – 6 stup obtnosti vetn 20 netradinch sudoku (zelen) (2014)

This Czech-language puzzle book contains 500 sudoku puzzles in six difficulty levels, including 20 entirely unconventional sudoku variants. It also explains that sudoku requires only paper, a pencil and an eraser, and describes how the originally American game, whose name comes from Japanese, became popular around the world.