MLA

Kilpatrick, Jack Frederick (1915-1967). Ayatasdi George. Letter. Box 17, folder 1454. 1945 April 2. https://collections.library.yale.edu/catalog/15532158.

APA, 6th edition

Kilpatrick, Jack Frederick (1915-1967). (["Box 17, folder 1454"])(1945 April 2)[Ayatasdi George. Letter]. https://collections.library.yale.edu/catalog/15532158.