MLA

Koch, Frederick R. (Frederick Robinson). Mignan, Edouard. Box 52, folder 1107. 1923 Jun 20. https://collections.library.yale.edu/catalog/2065838.

APA, 6th edition

Koch, Frederick R. (Frederick Robinson). (["Box 52, folder 1107"])(1923 Jun 20)[Mignan, Edouard]. https://collections.library.yale.edu/catalog/2065838.