MLA

Hughes, Langston, 1902-1967. Allen, James. Box 455, folder 10996. n.d.. https://collections.library.yale.edu/catalog/2014686.

APA, 6th edition

Hughes, Langston, 1902-1967. (["Box 455, folder 10996"])(n.d.)[Allen, James]. https://collections.library.yale.edu/catalog/2014686.