MLA

Argus Book Shop (Chicago, Ill.). Lewis, Sinclair. Box 7, folder 262. 1932-1940. https://collections.library.yale.edu/catalog/17411917.

APA, 6th edition

Argus Book Shop (Chicago, Ill.). (["Box 7, folder 262"])(1932-1940)[Lewis, Sinclair]. https://collections.library.yale.edu/catalog/17411917.