MLA

Hughes, Langston, 1902-1967. Guillen, Nicolas. Box 572, folder 13644. 1931. https://collections.library.yale.edu/catalog/17034208.

APA, 6th edition

Hughes, Langston, 1902-1967. (["Box 572, folder 13644"])(1931)[Guillen, Nicolas]. https://collections.library.yale.edu/catalog/17034208.