MLA

Brodsky, Joseph, 1940-1996. Vandermeer, Pieter. Box 142, folder 3150. undated. https://collections.library.yale.edu/catalog/2008151.

APA, 6th edition

Brodsky, Joseph, 1940-1996. (["Box 142, folder 3150"])(undated)[Vandermeer, Pieter]. https://collections.library.yale.edu/catalog/2008151.