MLA

McKay, Claude, 1890-1948. "H" General. Box 3, folder 91. 1926-40, n.d.. https://collections.library.yale.edu/catalog/10597749.

APA, 6th edition

McKay, Claude, 1890-1948. (["Box 3, folder 91"])(1926-40, n.d.)["H" General]. https://collections.library.yale.edu/catalog/10597749.