MLA

Nicolas, de Byard. Summa De Abstinentia. 0AD. https://collections.library.yale.edu/catalog/10622028.

APA, 6th edition

Nicolas, de B. (0 C.E.). Summa de abstinentia [Manuscripts, Medieval Italy 14th century, Medieval and Renaissance Manuscripts in Beinecke Library]. https://collections.library.yale.edu/catalog/10622028.