MLA

Jeleński, Konstanty A. (Konstanty Aleksander), 1922-1987. Unidentified essay in Polish, typescript. Box 10, folder 258. undated. https://collections.library.yale.edu/catalog/16612890.

APA, 6th edition

Jeleński, Konstanty A. (Konstanty Aleksander), 1922-1987. (["Box 10, folder 258"])(undated)[Unidentified essay in Polish, typescript]. https://collections.library.yale.edu/catalog/16612890.