MLA

Hughes, Langston, 1902-1967. Horne, Lena. Box 5 (Oversize), folder 69. 1958 May 6. https://collections.library.yale.edu/catalog/16198517.

APA, 6th edition

Hughes, Langston, 1902-1967. (["Box 5 (Oversize), folder 69"])(1958 May 6)[Horne, Lena]. https://collections.library.yale.edu/catalog/16198517.