MLA

Cullen, Countee, 1903-1946. Van Vechten, Carl. Box 2, folder 25. 1943 Nov 18. https://collections.library.yale.edu/catalog/16731071.

APA, 6th edition

Cullen, Countee, 1903-1946. (["Box 2, folder 25"])(1943 Nov 18)[Van Vechten, Carl]. https://collections.library.yale.edu/catalog/16731071.