MLA

Van Vechten, Carl, 1880-1964. Essen, Viola, as the Courtesan, with Kari Karnakoski as the Prince, and Francisco Moncion as Sebastian in Sebastian, ballet choreographed by Edward Caton. Box 90, folder 1566. 1944 November 20. https://collections.library.yale.edu/catalog/2026904.

APA, 6th edition

Van Vechten, Carl, 1880-1964. (["Box 90, folder 1566"])(1944 November 20)[Essen, Viola, as the Courtesan, with Kari Karnakoski as the Prince, and Francisco Moncion as Sebastian in Sebastian, ballet choreographed by Edward Caton]. https://collections.library.yale.edu/catalog/2026904.