MLA

Hughes, Langston, 1902-1967. "Black Nativity": London. Box 475, folder 11819-11820. n.d.. https://collections.library.yale.edu/catalog/2016997.

APA, 6th edition

Hughes, Langston, 1902-1967. (["Box 475, folder 11819-11820"])(n.d.)["Black Nativity": London]. https://collections.library.yale.edu/catalog/2016997.