Unidentified
MLA
McKay, Claude, 1890-1948. Unidentified. Box 18, folder 593-597a. 1920-35, n.d.. https://collections.library.yale.edu/catalog/2043849.
APA, 6th edition
McKay, Claude, 1890-1948. (["Box 18, folder 593-597a"])(1920-35, n.d.)[Unidentified]. https://collections.library.yale.edu/catalog/2043849.