MLA

Van Vechten, Carl, 1880-1964. Morgan, Helen, as Julie La Verne in Showboat, with music by Jerome Kern and book and lyrics by Oscar Hammerstein II. Box 368, folder 5184. 1932 June 23. https://collections.library.yale.edu/catalog/2067366.

APA, 6th edition

Van Vechten, Carl, 1880-1964. (["Box 368, folder 5184"])(1932 June 23)[Morgan, Helen, as Julie La Verne in Showboat, with music by Jerome Kern and book and lyrics by Oscar Hammerstein II]. https://collections.library.yale.edu/catalog/2067366.