MLA

Berberova, N. (Nina), 1901-1993. Karpovich, Michael. Box 57, folder 1299. 1926-35. https://collections.library.yale.edu/catalog/16688066.

APA, 6th edition

Berberova, N. (Nina), 1901-1993. (["Box 57, folder 1299"])(1926-35)[Karpovich, Michael]. https://collections.library.yale.edu/catalog/16688066.