MLA

Van Vechten, Carl, 1880-1964. Nabokov, Nicolas. Box 369, folder 5210. 1934 February 23. https://collections.library.yale.edu/catalog/2109321.

APA, 6th edition

Van Vechten, Carl, 1880-1964. (["Box 369, folder 5210"])(1934 February 23)[Nabokov, Nicolas]. https://collections.library.yale.edu/catalog/2109321.