Black Belt Kakuro: 150 PuzzlesPaperback, 1 August 2006

Kakuro language-free number puzzle that uses pure logic and requires just simple arithmetic to solve. This book is a part of a multilevel series of belt books, each containing 150 kakuros. These books take their cue from the belt colors in martial arts such as: white is for novices, and black for those consummate experts who crave a challenge.