MLA

Koch, Frederick R. (Frederick Robinson). Music/Malven. Box 335, folder 1931. 1948 Nov 23. https://collections.library.yale.edu/catalog/2002026.

APA, 6th edition

Koch, Frederick R. (Frederick Robinson). (["Box 335, folder 1931"])(1948 Nov 23)[Music/Malven]. https://collections.library.yale.edu/catalog/2002026.