We dedicate this book to the memory of Michael Downes (1958–2003), a great friend and wonderful colleague on the LaTeX Team. His thoughtful contributions to our work and our lives are diverse and profound. Moreover, he brightens the lives of countless grateful (La)TeX users through the wisdom built into his support for all aspects of mathematical typesetting—very many masterpieces of the publishing art will stand for ever as superb memorials to his quiet but deep insights.