Postings here occasionally note Aquinas’s use of Gratian (see here and here). Recently while tracking down some items in the Decretum I was surprised to find a wealth of online Gratian-related canon law resources. The 1582 Editio Romana of Gratian’s Decretum and the Glossa ordinaria are available in a wonderful format at UCLA’s digital canon law collection. (N.B.: the Glossa ordinaria on Gratian should not be confused with the 12th century commentary on the Latin vulgate with the same name). Emil Friedberg’s edition of Gratian’s work can be found in a variety of formats (e.g., 1, 2, 3). There are also assorted 19th-century editions of the Decretists on Gratian’s Decretum (e.g., Paucapalea, Rolandus, Rufinus, Stephen of Tournai) on various sites.
What other treasures have I missed?