MLA

Hughes, Langston, 1902-1967. Spanish Civil War, production of the play "La Tragedia Optimista," by Maria Teresa Leon. Box 460, folder 11139. n.d.. https://collections.library.yale.edu/catalog/10292960.

APA, 6th edition

Hughes, Langston, 1902-1967. (["Box 460, folder 11139"])(n.d.)[Spanish Civil War, production of the play "La Tragedia Optimista," by Maria Teresa Leon]. https://collections.library.yale.edu/catalog/10292960.