MLA

Koch, Frederick R. (Frederick Robinson). Music/La communion des Saints. Box 322, folder 1740. n.d.. https://collections.library.yale.edu/catalog/2007261.

APA, 6th edition

Koch, Frederick R. (Frederick Robinson). (["Box 322, folder 1740"])(n.d.)[Music/La communion des Saints]. https://collections.library.yale.edu/catalog/2007261.