Quadruplex psalter (fragment).
MLA
Quadruplex Psalter (Fragment). 12AD. https://collections.library.yale.edu/catalog/33093737.
APA, 6th edition
Quadruplex psalter (fragment). (12 C.E.). [Early works to 1800, Manuscripts, Medieval Germany 12th century, Medieval and Renaissance Manuscript Fragments in Beinecke Library, Medieval and Renaissance Manuscripts in Beinecke Library]. https://collections.library.yale.edu/catalog/33093737.