MLA

Koch, Frederick R. (Frederick Robinson). Bülow, Hans von. Box 59, folder 1346. 1868 Mar 13. https://collections.library.yale.edu/catalog/33264068.

APA, 6th edition

Koch, Frederick R. (Frederick Robinson). (["Box 59, folder 1346"])(1868 Mar 13)[Bülow, Hans von]. https://collections.library.yale.edu/catalog/33264068.