MLA

McKay, Claude, 1890-1948. Drafts, typescript and typescript carbon. Box 12, folder 372. n.d.. https://collections.library.yale.edu/catalog/15234679.

APA, 6th edition

McKay, Claude, 1890-1948. (["Box 12, folder 372"])(n.d.)[Drafts, typescript and typescript carbon]. https://collections.library.yale.edu/catalog/15234679.