MLA

Argus Book Shop (Chicago, Ill.). Cather, Willa. Box 2, folder 73. 1933. https://collections.library.yale.edu/catalog/33220158.

APA, 6th edition

Argus Book Shop (Chicago, Ill.). (["Box 2, folder 73"])(1933)[Cather, Willa]. https://collections.library.yale.edu/catalog/33220158.