MLA

Koch, Frederick R. (Frederick Robinson). Music/The Twelve. Box 340, folder 1993. 1965. https://collections.library.yale.edu/catalog/2019697.

APA, 6th edition

Koch, Frederick R. (Frederick Robinson). (["Box 340, folder 1993"])(1965)[Music/The Twelve]. https://collections.library.yale.edu/catalog/2019697.