MLA

Hughes, Langston, 1902-1967. Stratford Festival, Canada: press release. Box 481, folder 12128. ca. 1957. https://collections.library.yale.edu/catalog/17034175.

APA, 6th edition

Hughes, Langston, 1902-1967. (["Box 481, folder 12128"])(ca. 1957)[Stratford Festival, Canada: press release]. https://collections.library.yale.edu/catalog/17034175.