MLA

Hughes, Langston, 1902-1967. Allen, Betty. Box 5, folder 99. 1958-60, n.d.. https://collections.library.yale.edu/catalog/33090429.

APA, 6th edition

Hughes, Langston, 1902-1967. (["Box 5, folder 99"])(1958-60, n.d.)[Allen, Betty]. https://collections.library.yale.edu/catalog/33090429.