MLA

Wharton, Edith, 1862-1937. The Saturday Evening Post. Box 39, folder 1188. 1918-19. https://collections.library.yale.edu/catalog/17111175.

APA, 6th edition

Wharton, Edith, 1862-1937. (["Box 39, folder 1188"])(1918-19)[The Saturday Evening Post]. https://collections.library.yale.edu/catalog/17111175.