MLA

Cicero, Marcus Tullius. De Natura Deorum. 0AD. https://collections.library.yale.edu/catalog/11403234.

APA, 6th edition

Cicero, M. T. (0 C.E.). De natura deorum [Manuscripts, Medieval Italy 15th century, Medieval and Renaissance Manuscripts in Beinecke Library]. https://collections.library.yale.edu/catalog/11403234.