MLA

Psalter. 15AD. https://collections.library.yale.edu/catalog/2027184.

APA, 6th edition

Psalter. (15 C.E.). [Manuscripts, Medieval Italy 15th century, Medieval and Renaissance Manuscript Fragments in Beinecke Library, Medieval and Renaissance Manuscripts in Beinecke Library]. https://collections.library.yale.edu/catalog/2027184.