Cite

Thesaurus pauperum... [etc.]

MLA

John XXI, Pope, -1277. Thesaurus pauperum... [etc.]. between 1250 and 1399.. https://collections.library.yale.edu/catalog/16960318.

APA, 6th edition

John XXI, Pope, -1277. (between 1250 and 1399.)[Thesaurus pauperum... [etc.]]. https://collections.library.yale.edu/catalog/16960318.