MLA

Stein, Gertrude, 1874-1946. Kahnweiler, David-Henry. Box 137, folder 3152. 1946-53. https://collections.library.yale.edu/catalog/17105791.

APA, 6th edition

Stein, Gertrude, 1874-1946. (["Box 137, folder 3152"])(1946-53)[Kahnweiler, David-Henry]. https://collections.library.yale.edu/catalog/17105791.