MLA

Kilpatrick, Jack Frederick (1915-1967). Typed letter to John Comingdeer with handwritten response (in English). Box 11, folder 1020. 1911 May 12. https://collections.library.yale.edu/catalog/15493826.

APA, 6th edition

Kilpatrick, Jack Frederick (1915-1967). (["Box 11, folder 1020"])(1911 May 12)[Typed letter to John Comingdeer with handwritten response (in English)]. https://collections.library.yale.edu/catalog/15493826.