MLA

Van Thal, Herbert, 1904-1983. "P" general. Box 1, folder 89. 1965. https://collections.library.yale.edu/catalog/16545993.

APA, 6th edition

Van Thal, Herbert, 1904-1983. (["Box 1, folder 89"])(1965)["P" general]. https://collections.library.yale.edu/catalog/16545993.