MLA

Wat, Aleksander, 1900-1967. "Zeszyt 6," notebook. Box 33, folder 766. undated. https://collections.library.yale.edu/catalog/2054643.

APA, 6th edition

Wat, Aleksander, 1900-1967. (["Box 33, folder 766"])(undated)["Zeszyt 6," notebook]. https://collections.library.yale.edu/catalog/2054643.