Liber Extra
Like the former canonical collections, the Decretals of Gregory IX were soon glossed. It was customary to add to the manuscript copies textual explanations written between the lines ("glossa interlinearis") and on the margin of the page ("glossa marginalis"). Explanations of the subject-matter were also added. The most ancient glossarist of the Decretals of Gregory IX is Vincent of Spain; then follow Godefridus de Trano (died 1245), Bonaguida Aretinus (thirteenth century) and Bernard of Botone or Parmensis (died 1263), the author of the "Glossa ordinaria", i.e., of that gloss to which authoritative credence was generally given. At a later date some extracts were added to the "Glossa ordinaria" from the "Novella sive commentarius in decretales epistolas Gregorii IX" by Giovanni d'Andrea (Johannes Andreæ).