MLA

Holden, Reuben A. (Reuben Andrus), 1918-. Kingman Brewster. Box 1, folder 15. circa 1967-1968. https://collections.library.yale.edu/catalog/10011744.

APA, 6th edition

Holden, Reuben A. (Reuben Andrus), 1918-. (["Box 1, folder 15"])(circa 1967-1968)[Kingman Brewster]. https://collections.library.yale.edu/catalog/10011744.