MLA

Theodoret, Bishop of Cyrrhus. Eranistes (Polymorphos). 0AD. https://collections.library.yale.edu/catalog/9999009.

APA, 6th edition

Theodoret, B. of C. (0 C.E.). Eranistes (Polymorphos). [Manuscripts, Renaissance Italy 16th century, Medieval and Renaissance Manuscripts in Beinecke Library]. https://collections.library.yale.edu/catalog/9999009.