MLA

Whitman, Walt, 1819-1892. Woodcut block. Art, folder 206. n.d.. https://collections.library.yale.edu/catalog/2011859.

APA, 6th edition

Whitman, Walt, 1819-1892. (["Art, folder 206"])(n.d.)[Woodcut block]. https://collections.library.yale.edu/catalog/2011859.