MLA

Hughes, Langston, 1902-1967. "Common Ground": speaking tour, letters from high school. Box 212, folder 3578. 1944, n.d.. https://collections.library.yale.edu/catalog/2043794.

APA, 6th edition

Hughes, Langston, 1902-1967. (["Box 212, folder 3578"])(1944, n.d.)["Common Ground": speaking tour, letters from high school]. https://collections.library.yale.edu/catalog/2043794.