MLA

Van Vechten, Carl, 1880-1964. Essen, Viola, as the Princess, in Sebastian, ballet choreographed by Edward Caton. Box 403 | Folder 6260. 1944 November 20. https://collections.library.yale.edu/catalog/2034270.

APA, 6th edition

Van Vechten, Carl, 1880-1964. (["Box 403 | Folder 6260"])(1944 November 20)[Essen, Viola, as the Princess, in Sebastian, ballet choreographed by Edward Caton]. https://collections.library.yale.edu/catalog/2034270.