MLA

Schaefer, F. L. Chronic Mitral Endocarditis. 1918. https://collections.library.yale.edu/catalog/15948090.

APA, 6th edition

Schaefer, F. L. (1918). Chronic Mitral Endocarditis [Drawings (AAT)]. https://collections.library.yale.edu/catalog/15948090.