MLA

Portius, Agapitus, fl. 15th cent. Epistolae. [ca. 1474-75]. https://collections.library.yale.edu/catalog/2042572.

APA, 6th edition

Portius, Agapitus, fl. 15th cent. ([ca. 1474-75])[Epistolae]. https://collections.library.yale.edu/catalog/2042572.