MLA

Koch, Frederick R. (Frederick Robinson). Magrini, Erminia. Box 49, folder 1045. 1921 Jan-Aug. https://collections.library.yale.edu/catalog/16064686.

APA, 6th edition

Koch, Frederick R. (Frederick Robinson). (["Box 49, folder 1045"])(1921 Jan-Aug)[Magrini, Erminia]. https://collections.library.yale.edu/catalog/16064686.