MLA

Whitman, Walt, 1819-1892. Printed version, Century Magazine. Box 3, folder 160. [1911 Feb]. https://collections.library.yale.edu/catalog/2053792.

APA, 6th edition

Whitman, Walt, 1819-1892. (["Box 3, folder 160"])([1911 Feb])[Printed version, Century Magazine]. https://collections.library.yale.edu/catalog/2053792.