MLA

Schwartz, Delmore, 1913-1966. Abraham and Orpheus. Box 3, folder 148. undated. https://collections.library.yale.edu/catalog/17405208.

APA, 6th edition

Schwartz, Delmore, 1913-1966. (["Box 3, folder 148"])(undated)[Abraham and Orpheus]. https://collections.library.yale.edu/catalog/17405208.