MLA

Whitman, Walt, 1819-1892. J. Jusko bronze medallion. Art, folder 189. n.d.. https://collections.library.yale.edu/catalog/2011861.

APA, 6th edition

Whitman, Walt, 1819-1892. (["Art, folder 189"])(n.d.)[J. Jusko bronze medallion]. https://collections.library.yale.edu/catalog/2011861.