MLA

Jeleński, Konstanty A. (Konstanty Aleksander), 1922-1987. Nabokov, Nicolas to Konstanty Jeleński. Box 13, folder 294. 1967 February 28. https://collections.library.yale.edu/catalog/16612891.

APA, 6th edition

Jeleński, Konstanty A. (Konstanty Aleksander), 1922-1987. (["Box 13, folder 294"])(1967 February 28)[Nabokov, Nicolas to Konstanty Jeleński]. https://collections.library.yale.edu/catalog/16612891.