MLA

Hughes, Langston, 1902-1967. New Negro Poets: USA. Box 537, folder 13199. 1964, n.d.. https://collections.library.yale.edu/catalog/2065321.

APA, 6th edition

Hughes, Langston, 1902-1967. (["Box 537, folder 13199"])(1964, n.d.)[New Negro Poets: USA]. https://collections.library.yale.edu/catalog/2065321.