MLA

Van Vechten, Carl, 1880-1964. McCullers, Carson. Box 485, folder 8519-8520. 1959 July 31. https://collections.library.yale.edu/catalog/2065511.

APA, 6th edition

Van Vechten, Carl, 1880-1964. (["Box 485, folder 8519-8520"])(1959 July 31)[McCullers, Carson]. https://collections.library.yale.edu/catalog/2065511.