Asimov, I. (1989). Frontiers: New discoveries about man and his planet, outer space, and the universe. Plume.
Chicago-referens (17:e uppl.)Asimov, Isaac. Frontiers: New Discoveries About Man and His Planet, Outer Space, and the Universe. New York: Plume, 1989.
MLA-referens (9:e uppl.)Asimov, Isaac. Frontiers: New Discoveries About Man and His Planet, Outer Space, and the Universe. Plume, 1989.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.