MLA

Koch, Frederick R. (Frederick Robinson). Hirt, Franz Josef. Box 51, folder 1100. 1927 Jan 23. https://collections.library.yale.edu/catalog/2065834.

APA, 6th edition

Koch, Frederick R. (Frederick Robinson). (["Box 51, folder 1100"])(1927 Jan 23)[Hirt, Franz Josef]. https://collections.library.yale.edu/catalog/2065834.