MLA

Schwartz, Delmore, 1913-1966. "Birth, Copulation, Death". Box 3, folder 153. undated. https://collections.library.yale.edu/catalog/17078928.

APA, 6th edition

Schwartz, Delmore, 1913-1966. (["Box 3, folder 153"])(undated)["Birth, Copulation, Death"]. https://collections.library.yale.edu/catalog/17078928.