MLA

Stein, Gertrude, 1874-1946. About Gertrude Stein. Box 142, folder 3333-3335. 1913-18. https://collections.library.yale.edu/catalog/2112322.

APA, 6th edition

Stein, Gertrude, 1874-1946. (["Box 142, folder 3333-3335"])(1913-18)[About Gertrude Stein]. https://collections.library.yale.edu/catalog/2112322.