MLA

Schwartz, Delmore, 1913-1966. Trilling, Lionel. Box 1, folder 117. 1954 December 21. https://collections.library.yale.edu/catalog/17078926.

APA, 6th edition

Schwartz, Delmore, 1913-1966. (["Box 1, folder 117"])(1954 December 21)[Trilling, Lionel]. https://collections.library.yale.edu/catalog/17078926.