MLA

Cicero, Marcus Tullius. Epistolae Ad Familiares. 0AD. https://collections.library.yale.edu/catalog/10269813.

APA, 6th edition

Cicero, M. T. (0 C.E.). Epistolae ad familiares [Manuscripts, Medieval Italy 15th century, Manuscripts, Medieval Netherlands 15th century, Medieval and Renaissance Manuscripts in Beinecke Library]. https://collections.library.yale.edu/catalog/10269813.