MLA

Koch, Frederick R. (Frederick Robinson). Album amicorum. Box 21, folder 425-426. 1919-20, n.d.. https://collections.library.yale.edu/catalog/2020946.

APA, 6th edition

Koch, Frederick R. (Frederick Robinson). (["Box 21, folder 425-426"])(1919-20, n.d.)[Album amicorum]. https://collections.library.yale.edu/catalog/2020946.