MLA

Amalarius, Archbishop of Lyon, approximately 775-approximately 850. Liber officialis (fragment).. approximately 1050-approximately 1075.. https://collections.library.yale.edu/catalog/10543812.

APA, 6th edition

Amalarius, Archbishop of Lyon, approximately 775-approximately 850. (approximately 1050-approximately 1075.)[Liber officialis (fragment).]. https://collections.library.yale.edu/catalog/10543812.