MLA

Whitman, Walt, 1819-1892. Confederate bill. Box 4, folder 198. 1864 Feb 17. https://collections.library.yale.edu/catalog/2053827.

APA, 6th edition

Whitman, Walt, 1819-1892. (["Box 4, folder 198"])(1864 Feb 17)[Confederate bill]. https://collections.library.yale.edu/catalog/2053827.