MLA

Stein, Gertrude, 1874-1946. Brooks, Romaine. Box 99, folder 1914. 1934, n.d.. https://collections.library.yale.edu/catalog/2003361.

APA, 6th edition

Stein, Gertrude, 1874-1946. (["Box 99, folder 1914"])(1934, n.d.)[Brooks, Romaine]. https://collections.library.yale.edu/catalog/2003361.