[Letter : 1967 March 6, Washington (D.C.), Smithsonian Institution to Saul Steinberg, Washington (D.C.)]
MLA
Institution, Smithsonian. [Letter : 1967 March 6, Washington (D.C.), Smithsonian Institution to Saul Steinberg, Washington (D.C.)]. 1967. https://collections.library.yale.edu/catalog/10056891.
APA, 6th edition
Institution, S. (1967). [Letter : 1967 March 6, Washington (D.C.), Smithsonian Institution to Saul Steinberg, Washington (D.C.)] [Correspondence]. https://collections.library.yale.edu/catalog/10056891.