Liber Extra
To indicate the principal commentators on the Decretals would mean writing a history of canon law in the Middle Ages. Important canonists include Innocent IV (died 1254), Enrico de Segusio or Hostiensis (died 1271), the "Abbas antiquus" (thirteenth century), Johannes Andreæ, Baldus de Ubaldis (died 1400), Petrus de Ancharano (died 1416), Franciscus de Zabarellis (died 1417), Dominicus a Sancto Geminiano (fifteenth century), Joannes de Imola (died 1436) and Nicolò Tudesco also called the "Abbas Siculus", or "Modernus", or "Panormitanus" (died 1453). Among the modern commentators, Manuel Gonzalez Tellez and Fagnanus may be consulted advantageously for the interpretation of the text of the Decretals. The Decretals of Gregory IX remain the basis of canon law so far as it has not been modified by subsequent collections and by the general laws of the Church (see Corpus Juris Canonici).