MLA

Holden, Reuben A. (Reuben Andrus), 1918-. Charles Seymour. Box 1, folder 13. circa 1967-1968. https://collections.library.yale.edu/catalog/10011741.

APA, 6th edition

Holden, Reuben A. (Reuben Andrus), 1918-. (["Box 1, folder 13"])(circa 1967-1968)[Charles Seymour]. https://collections.library.yale.edu/catalog/10011741.