MLA

Peter Riga, ca. 1140-1209. Aurora. [between 1200 and 1299]. https://collections.library.yale.edu/catalog/11007511.

APA, 6th edition

Peter Riga, ca. 1140-1209. ([between 1200 and 1299])[Aurora]. https://collections.library.yale.edu/catalog/11007511.