White Belt Kakuro: 150 PuzzlesPaperback, 1 August 2006

Kakuro are language-free number puzzles that use pure logic and require just simple arithmetic to solve. This book contains 150 kakuros. It takes cue from the belt colors in martial arts: white is for novices, green for intermediates, brown for very accomplished players, and black for those consummate experts who crave a challenge.