One of the masters in the differential equations community, the late F.V. Atkinson contributed seminal research to multiparameter spectral theory and Sturm-Liouville theory for more than 40 years. His ideas and techniques have long inspired researchers and continue to stimulate discussion. With the help of co-author Angelo B. Mingarelli, this book reflects much of Dr. Atkinson¿s final work. It covers the full multiparameter theory as applied to second-order linear equations and considers the spectral theory of multiparameter problems in detail for both regular and singular cases. Examples are illustrated using Maple¿.