MLA

Holden, Reuben A. (Reuben Andrus), 1918-. Noah Porter. Box 1, folder 9. circa 1967-1968. https://collections.library.yale.edu/catalog/10011735.

APA, 6th edition

Holden, Reuben A. (Reuben Andrus), 1918-. (["Box 1, folder 9"])(circa 1967-1968)[Noah Porter]. https://collections.library.yale.edu/catalog/10011735.