Bonaventura was a Franciscan monk living in Brescia at the end of the fifteenth century. His short theoretical treatise includes a chapter devoted to differentiae, "Concerning the terminals of the tones" (Chapter 37). Bonaventura only includes one differentia per mode, potentially indicating an attempt to standardize the system of differentiae.
Bonaventura da Brescia, Brevis collectio artis musicae, ed. Albert Seay, Critical Texts, no. 11 (Colorado Springs: Colorado College Music Press, 1980).