MLA

Stein, Gertrude, 1874-1946. Balmain, Pierre. Box 136, folder 3080. [1946] Oct 22. https://collections.library.yale.edu/catalog/10734391.

APA, 6th edition

Stein, Gertrude, 1874-1946. (["Box 136, folder 3080"])([1946] Oct 22)[Balmain, Pierre]. https://collections.library.yale.edu/catalog/10734391.