The authors thank Michael Weitz for his role in the planning of this edition and Regina Y. Brown for her key role in preparing it for publication. We also thank Shruti Awasthi of Cenveo Publisher Services for her efforts in editing, typesetting, and artwork. Suggestions from students and colleagues around the world have been most helpful in the formulation of this edition. We look forward to receiving similar input in the future. Finally, we acknowledge Robert Murray for his leadership and contributions to prior editions of this book.