MLA

Koch, Frederick R. (Frederick Robinson). Burghauser, Hugo. Box 57, folder 1258. 1949-66, n.d.. https://collections.library.yale.edu/catalog/16601862.

APA, 6th edition

Koch, Frederick R. (Frederick Robinson). (["Box 57, folder 1258"])(1949-66, n.d.)[Burghauser, Hugo]. https://collections.library.yale.edu/catalog/16601862.