MLA

Stein, Gertrude, 1874-1946. Alvin Langdon Coburn. Box 152, folder 3660-3661. 1912-13. https://collections.library.yale.edu/catalog/2011591.

APA, 6th edition

Stein, Gertrude, 1874-1946. (["Box 152, folder 3660-3661"])(1912-13)[Alvin Langdon Coburn]. https://collections.library.yale.edu/catalog/2011591.