MLA

Alexander, de Villa Dei. Doctrinale. 0AD. https://collections.library.yale.edu/catalog/11403200.

APA, 6th edition

Alexander, de V. D. (0 C.E.). Doctrinale [Manuscripts, Medieval Italy 15th century, Medieval and Renaissance Manuscripts in Beinecke Library]. https://collections.library.yale.edu/catalog/11403200.