MLA

Berberova, N. (Nina), 1901-1993. Berberov, Nikolai Berberova, Natalia. Box 4, folder 61. 1927-4?, n.d.. https://collections.library.yale.edu/catalog/16687983.

APA, 6th edition

Berberova, N. (Nina), 1901-1993. (["Box 4, folder 61"])(1927-4?, n.d.)[Berberov, Nikolai Berberova, Natalia]. https://collections.library.yale.edu/catalog/16687983.