MLA

Hughes, Langston, 1902-1967. Urrutia, Gustavo E.. Box 472, folder 11732. 1930 Mar 7. https://collections.library.yale.edu/catalog/2043769.

APA, 6th edition

Hughes, Langston, 1902-1967. (["Box 472, folder 11732"])(1930 Mar 7)[Urrutia, Gustavo E.]. https://collections.library.yale.edu/catalog/2043769.