MLA

Hughes, Langston, 1902-1967. Walker, Margaret. Box 21, folder 320. 1978. https://collections.library.yale.edu/catalog/16207097.

APA, 6th edition

Hughes, Langston, 1902-1967. (["Box 21, folder 320"])(1978)[Walker, Margaret]. https://collections.library.yale.edu/catalog/16207097.