MLA

McKay, Claude, 1890-1948. France. Box 16, folder 494. n.d.. https://collections.library.yale.edu/catalog/16742370.

APA, 6th edition

McKay, Claude, 1890-1948. (["Box 16, folder 494"])(n.d.)[France]. https://collections.library.yale.edu/catalog/16742370.