MLA

Speculum Christiani. 0AD. https://collections.library.yale.edu/catalog/15605268.

APA, 6th edition

Speculum Christiani. (0 C.E.). [Early works to 1800, Handbooks, manuals, etc, Manuscripts, Medieval England 15th century, Medieval and Renaissance Manuscripts in Beinecke Library]. https://collections.library.yale.edu/catalog/15605268.