MLA

Stein, Leo, 1872-1947. Weeks, Mabel Foote. Box 3, folder 51-59. 1900-1947, n.d.. https://collections.library.yale.edu/catalog/17155340.

APA, 6th edition

Stein, Leo, 1872-1947. (["Box 3, folder 51-59"])(1900-1947, n.d.)[Weeks, Mabel Foote]. https://collections.library.yale.edu/catalog/17155340.