MLA

Schwartz, Delmore, 1913-1966. "Swift". Box 3, folder 205. undated. https://collections.library.yale.edu/catalog/17405248.

APA, 6th edition

Schwartz, Delmore, 1913-1966. (["Box 3, folder 205"])(undated)["Swift"]. https://collections.library.yale.edu/catalog/17405248.