MLA

McKay, Claude, 1890-1948. Schomburg, Arthur Alfonso. Box 6, folder 192. 1925-35. https://collections.library.yale.edu/catalog/16742359.

APA, 6th edition

McKay, Claude, 1890-1948. (["Box 6, folder 192"])(1925-35)[Schomburg, Arthur Alfonso]. https://collections.library.yale.edu/catalog/16742359.