MLA

Sergeant, Elizabeth Shepley, 1881-1965. Notebooks. Box 19, folder 406-07. n.d.. https://collections.library.yale.edu/catalog/10544373.

APA, 6th edition

Sergeant, Elizabeth Shepley, 1881-1965. (["Box 19, folder 406-07"])(n.d.)[Notebooks]. https://collections.library.yale.edu/catalog/10544373.