MLA

Brodsky, Joseph, 1940-1996. Tomashevskaia, Anastasia. Box 15, folder 397. 1960s. https://collections.library.yale.edu/catalog/2107227.

APA, 6th edition

Brodsky, Joseph, 1940-1996. (["Box 15, folder 397"])(1960s)[Tomashevskaia, Anastasia]. https://collections.library.yale.edu/catalog/2107227.