MLA

Whitman, Walt, 1819-1892. "Inscription," holograph. Box 3, folder 154. [ca. 1867?]. https://collections.library.yale.edu/catalog/2001536.

APA, 6th edition

Whitman, Walt, 1819-1892. (["Box 3, folder 154"])([ca. 1867?])["Inscription," holograph]. https://collections.library.yale.edu/catalog/2001536.