MLA

Gradual. 13AD. https://collections.library.yale.edu/catalog/10518833.

APA, 6th edition

Gradual. (13 C.E.). [Manuscripts, Medieval Italy 13th century, Medieval and Renaissance Manuscript Fragments in Beinecke Library, Medieval and Renaissance Manuscripts in Beinecke Library]. https://collections.library.yale.edu/catalog/10518833.