Wilfried Hartmann is emeritus professor of the medieval history of canon law at the University of Tbingen. Kenneth Pennington is Kelly-Quinn Professor of Ecclesiastical and Legal History at The Catholic University of America. He is the author of numerous works including Pope and Bishops: The Papal Monarchy in the Twelfth and Thirteenth Centuries and The Prince and the Law, 1200-1600: Sovereignty and Rights in the Western Legal Tradition. Hartmann and Pennington are coeditors of the History of Medieval Canon Law series.