MLA

Hughes, Langston, 1902-1967. Marco, Pedro. Box 469, folder 11588. 1931. https://collections.library.yale.edu/catalog/33548721.

APA, 6th edition

Hughes, Langston, 1902-1967. (["Box 469, folder 11588"])(1931)[Marco, Pedro]. https://collections.library.yale.edu/catalog/33548721.