MLA

Stein, Leo, 1872-1947. Stein, Leo. Box 14, folder 357. 1927-28, n.d.. https://collections.library.yale.edu/catalog/2041964.

APA, 6th edition

Stein, Leo, 1872-1947. (["Box 14, folder 357"])(1927-28, n.d.)[Stein, Leo]. https://collections.library.yale.edu/catalog/2041964.