MLA

Church, Catholic. Gradual. 0AD. https://collections.library.yale.edu/catalog/10675700.

APA, 6th edition

Church, C. (0 C.E.). Gradual [Manuscripts, Medieval Switzerland 13th century, Manuscripts, Medieval Switzerland 14th century, Medieval and Renaissance Manuscripts in Beinecke Library]. https://collections.library.yale.edu/catalog/10675700.