MLA

Hughes, Langston, 1902-1967. Pushkin, Aleksandr Sergeevich. Box 20, folder 293. 1875-1978. https://collections.library.yale.edu/catalog/16207070.

APA, 6th edition

Hughes, Langston, 1902-1967. (["Box 20, folder 293"])(1875-1978)[Pushkin, Aleksandr Sergeevich]. https://collections.library.yale.edu/catalog/16207070.