MLA

Koch, Frederick R. (Frederick Robinson). Hoeck, Mary. Box 5, folder 133. 1949. https://collections.library.yale.edu/catalog/16601827.

APA, 6th edition

Koch, Frederick R. (Frederick Robinson). (["Box 5, folder 133"])(1949)[Hoeck, Mary]. https://collections.library.yale.edu/catalog/16601827.