As a teacher at the University in Bologna sometime between 1140 and 1150, Gratian, who was also a monk, organized the study of church law with his compilation of the Decretum. This unprecedented gathering of nearly four thousand texts was drawn from Early Christian writings, papal pronouncements, and council decrees. As the most comprehensive manual of canon law, it quickly became a standard textbook for university students throughout Europe. The Getty Museum's manuscript of the Decretum, dated about 1170 to 1180, is richly illuminated, with two full-page miniatures and a variety of historiated and decorated initials that mark divisions of the text. The northern French Romanesque style of the illuminations was strongly influenced by English art. This type of decoration links the manuscript to a group of books produced for Thomas Becket, Archbishop of Canterbury, and his secretary while they were in exile in France. Made by anonymous craftspeople, it is not clear whether the Museum's manuscript and the other books in this group were painted in Sens, the site of Becket's exile, or in nearby Paris.