MLA

Korvin-Piotrovskiĭ, Vladimir Lʹvovich, 1891-1966. Sovremennye Zapiski. Box 2, folder 47. undated. https://collections.library.yale.edu/catalog/16601457.

APA, 6th edition

Korvin-Piotrovskiĭ, Vladimir Lʹvovich, 1891-1966. (["Box 2, folder 47"])(undated)[Sovremennye Zapiski]. https://collections.library.yale.edu/catalog/16601457.