MLA

Wescott, Glenway, 1901-1987. Montgomery, George. Box 400, folder 4090. n.d.. https://collections.library.yale.edu/catalog/17065037.

APA, 6th edition

Wescott, Glenway, 1901-1987. (["Box 400, folder 4090"])(n.d.)[Montgomery, George]. https://collections.library.yale.edu/catalog/17065037.