MLA

Hughes, Langston, 1902-1967. Garner, Sylvia. Box 468, folder 11456. n.d.. https://collections.library.yale.edu/catalog/2019981.

APA, 6th edition

Hughes, Langston, 1902-1967. (["Box 468, folder 11456"])(n.d.)[Garner, Sylvia]. https://collections.library.yale.edu/catalog/2019981.