MLA

Berberova, N. (Nina), 1901-1993. Dutton, Richard. Box 54, folder 1232. 1980, n.d.. https://collections.library.yale.edu/catalog/10454445.

APA, 6th edition

Berberova, N. (Nina), 1901-1993. (["Box 54, folder 1232"])(1980, n.d.)[Dutton, Richard]. https://collections.library.yale.edu/catalog/10454445.