The Harder They Come Sudoku Schwierige Rätsel (240 + Rätsel): Puzzle Therapist
Solve Extreme Sudoku:Strategies for Easy to Hard Puzzles Robert Emmert, Scott Gandert
KenKen has quickly become the successor to sudoku that the world´s been waiting for! KenKen became the first puzzles to be printed in the daily editions of the New York Times next to its famous crossword puzzle. This New York Times edition of KenKen contains 300 4x4 and 6x6 size puzzles with ´´How to Solve´´ instructions and an introduction by puzzlemaster Will Shortz. The puzzles use all four mathematical operations and increase in difficulty like they do in the Times.