MLA

Koch, Frederick R. (Frederick Robinson). Delahaye, Ernest. Box 58, folder 1327. [1873 May 15]. https://collections.library.yale.edu/catalog/2020941.

APA, 6th edition

Koch, Frederick R. (Frederick Robinson). (["Box 58, folder 1327"])([1873 May 15])[Delahaye, Ernest]. https://collections.library.yale.edu/catalog/2020941.