MLA

Van Vechten, Carl, 1880-1964. Poems and plays. Box 188, folder 2508. 1914, 1915, undated. https://collections.library.yale.edu/catalog/2112213.

APA, 6th edition

Van Vechten, Carl, 1880-1964. (["Box 188, folder 2508"])(1914, 1915, undated)[Poems and plays]. https://collections.library.yale.edu/catalog/2112213.