MLA

Severus, Sulpicius. 1500?. De vita B. Martini episcopi Turonensis ; Symeonis Metaphrastis De vita B. Nicolai episcopi Myrensis / [translated into Latin by Leonardo Giustiniani].. ca. (or rather, after?) 1500]. https://collections.library.yale.edu/catalog/17451990.

APA, 6th edition

Severus, Sulpicius. 1500?. (ca. (or rather, after?) 1500])[De vita B. Martini episcopi Turonensis ; Symeonis Metaphrastis De vita B. Nicolai episcopi Myrensis / [translated into Latin by Leonardo Giustiniani].]. https://collections.library.yale.edu/catalog/17451990.