MLA

Koch, Frederick R. (Frederick Robinson). Chevalier, Louis. Box 48, folder 975. [1956]-62, n.d.. https://collections.library.yale.edu/catalog/16601846.

APA, 6th edition

Koch, Frederick R. (Frederick Robinson). (["Box 48, folder 975"])([1956]-62, n.d.)[Chevalier, Louis]. https://collections.library.yale.edu/catalog/16601846.