MLA

Koch, Frederick R. (Frederick Robinson). Vocal line. Box 61, folder 1396. n.d.. https://collections.library.yale.edu/catalog/2043646.

APA, 6th edition

Koch, Frederick R. (Frederick Robinson). (["Box 61, folder 1396"])(n.d.)[Vocal line]. https://collections.library.yale.edu/catalog/2043646.