New York Post Train Your Brain Su Doku:

The official utterly addictive number-placing puzzle Give your brain a workout with these all new Fiendishly tough puzzles. Their addictive power will not only entertain--Su Doku puzzles engage your mind, improve your concentration, and help you stay mentally fit. There's no excuse for slow thinking and flabby wits when you can train your brain! Beware of pale imitations. These are the original and official Su Doku puzzles by Wayne Gould--"New York Post"'s Su Doku puzzle master and one of "Time" magazine's Most Influential People.