MLA

McKay, Claude, 1890-1948. Walrond, Eric. Box 7, folder 227. 1927. https://collections.library.yale.edu/catalog/16742360.

APA, 6th edition

McKay, Claude, 1890-1948. (["Box 7, folder 227"])(1927)[Walrond, Eric]. https://collections.library.yale.edu/catalog/16742360.