MLA

Whitman, Walt, 1819-1892. "Shak[e]spe[a]re-Bacon's Cipher," galley proof. Box 1, folder 47. n.d.. https://collections.library.yale.edu/catalog/2053681.

APA, 6th edition

Whitman, Walt, 1819-1892. (["Box 1, folder 47"])(n.d.)["Shak[e]spe[a]re-Bacon's Cipher," galley proof]. https://collections.library.yale.edu/catalog/2053681.