MLA

Kuh, Katharine, 1904-1994. Ernst, Max. Box 1, folder 8. n.d.. https://collections.library.yale.edu/catalog/33066996.

APA, 6th edition

Kuh, Katharine, 1904-1994. (["Box 1, folder 8"])(n.d.)[Ernst, Max]. https://collections.library.yale.edu/catalog/33066996.