"The 85 Ways to Tie a Tie", (with Yong Mao, Fourth Estate, London) is a cultural, historical and mathematical examination of ties and tie knots. It explains how the authors proved mathematically that there are a total of 85 distinct tie knots, most of which had not been previously known. The book includes a layman's account of the authors' mathematical papers which derived all possible knots capable of being tied with a standard necktie. It has been published in 10 languages, including French, German, Hungarian, Portuguese and Italian.