MLA

Koch, Frederick R. (Frederick Robinson). Reber, Henri. Box 59, folder 1338. n.d.. https://collections.library.yale.edu/catalog/16601870.

APA, 6th edition

Koch, Frederick R. (Frederick Robinson). (["Box 59, folder 1338"])(n.d.)[Reber, Henri]. https://collections.library.yale.edu/catalog/16601870.