Printed ephemera
MLA
Whitman, Walt, 1819-1892. Printed ephemera. Box 4, folder 204. [1880], n.d.. https://collections.library.yale.edu/catalog/2053833.
APA, 6th edition
Whitman, Walt, 1819-1892. (["Box 4, folder 204"])([1880], n.d.)[Printed ephemera]. https://collections.library.yale.edu/catalog/2053833.