MLA

Whitman, Walt, 1819-1892. Notes and Fragments, extracts, typescript. Box 1, folder 15. n.d.. https://collections.library.yale.edu/catalog/2053649.

APA, 6th edition

Whitman, Walt, 1819-1892. (["Box 1, folder 15"])(n.d.)[Notes and Fragments, extracts, typescript]. https://collections.library.yale.edu/catalog/2053649.