MLA

Schwartz, Delmore, 1913-1966. "Summer Knowledge". Box 3, folder 190-191. 1959, undated. https://collections.library.yale.edu/catalog/17405238.

APA, 6th edition

Schwartz, Delmore, 1913-1966. (["Box 3, folder 190-191"])(1959, undated)["Summer Knowledge"]. https://collections.library.yale.edu/catalog/17405238.