MLA

Brodsky, Joseph, 1940-1996. Sharymova, Natalia. Box 142, folder 3147-3148. undated. https://collections.library.yale.edu/catalog/2008159.

APA, 6th edition

Brodsky, Joseph, 1940-1996. (["Box 142, folder 3147-3148"])(undated)[Sharymova, Natalia]. https://collections.library.yale.edu/catalog/2008159.