MLA

Zilboorg, Gregory, 1890-1959. Research notes. Box 3, folder 38-41. undated. https://collections.library.yale.edu/catalog/17085344.

APA, 6th edition

Zilboorg, Gregory, 1890-1959. (["Box 3, folder 38-41"])(undated)[Research notes]. https://collections.library.yale.edu/catalog/17085344.