MLA

Hulme, Kathryn, 1900-1981. "American Spas". Box 5, folder 100. 1942. https://collections.library.yale.edu/catalog/32472211.

APA, 6th edition

Hulme, Kathryn, 1900-1981. (["Box 5, folder 100"])(1942)["American Spas"]. https://collections.library.yale.edu/catalog/32472211.