MLA

Stein, Gertrude, 1874-1946. Printed version, Saturday Evening Post. Box 168, folder 4308. 1936 Aug 22. https://collections.library.yale.edu/catalog/2065769.

APA, 6th edition

Stein, Gertrude, 1874-1946. (["Box 168, folder 4308"])(1936 Aug 22)[Printed version, Saturday Evening Post]. https://collections.library.yale.edu/catalog/2065769.