MLA

Koch, Frederick R. (Frederick Robinson). Music/Polka. Box 329, folder 1843. n.d.. https://collections.library.yale.edu/catalog/12218312.

APA, 6th edition

Koch, Frederick R. (Frederick Robinson). (["Box 329, folder 1843"])(n.d.)[Music/Polka]. https://collections.library.yale.edu/catalog/12218312.