MLA

Van Vechten, Carl, 1880-1964. Knopf, Alfred A., Jr. Box 357, folder 4858. 1932 June 21. https://collections.library.yale.edu/catalog/2054936.

APA, 6th edition

Van Vechten, Carl, 1880-1964. (["Box 357, folder 4858"])(1932 June 21)[Knopf, Alfred A., Jr]. https://collections.library.yale.edu/catalog/2054936.