MLA

Kilpatrick, Jack Frederick (1915-1967). Robbins, Price. Postcard to Jack Nofire. Box 14, folder 1228. 1957 October 8. https://collections.library.yale.edu/catalog/15530863.

APA, 6th edition

Kilpatrick, Jack Frederick (1915-1967). (["Box 14, folder 1228"])(1957 October 8)[Robbins, Price. Postcard to Jack Nofire]. https://collections.library.yale.edu/catalog/15530863.