MLA

Berberova, N. (Nina), 1901-1993. TSvetaeva, Marina Ivanovna. Box 57, folder 1318. 1933-37, n.d.. https://collections.library.yale.edu/catalog/16689882.

APA, 6th edition

Berberova, N. (Nina), 1901-1993. (["Box 57, folder 1318"])(1933-37, n.d.)[TSvetaeva, Marina Ivanovna]. https://collections.library.yale.edu/catalog/16689882.