MLA

Antiphonary or Breviary (Fragment). 12AD. https://collections.library.yale.edu/catalog/10543818.

APA, 6th edition

Antiphonary or breviary (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/10543818.