Hobbs, R. C., & Smithson, R. (1981). Robert Smithson: Sculpture / Robert Carleton Hobbs. With contrib. by. Cornell Univ. Press.
Lua i Stíl Chicago (17ú heag.)Hobbs, Robert Carleton, agus Robert Smithson. Robert Smithson: Sculpture / Robert Carleton Hobbs. With Contrib. by. Ithaca [u.a.]: Cornell Univ. Press, 1981.
Lua MLA (8ú heag.)Hobbs, Robert Carleton, agus Robert Smithson. Robert Smithson: Sculpture / Robert Carleton Hobbs. With Contrib. by. Cornell Univ. Press, 1981.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.