Asimov, I. (1989). Frontiers: New discoveries about man and his planet, outer space, and the universe. Plume.
Lua i Stíl Chicago (17ú heag.)Asimov, Isaac. Frontiers: New Discoveries About Man and His Planet, Outer Space, and the Universe. New York: Plume, 1989.
Lua MLA (9ú heag.)Asimov, Isaac. Frontiers: New Discoveries About Man and His Planet, Outer Space, and the Universe. Plume, 1989.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.