Asimov, I. (1989). Frontiers: New discoveries about man and his planet, outer space, and the universe. Plume.
Chicago-čujuhus (17. p.)Asimov, Isaac. Frontiers: New Discoveries About Man and His Planet, Outer Space, and the Universe. New York: Plume, 1989.
MLA-čujuhus (9. p.)Asimov, Isaac. Frontiers: New Discoveries About Man and His Planet, Outer Space, and the Universe. Plume, 1989.
Muitte dárkkistit čujuhemiid riektatvuođa, ovdal go geavahat daid iežat deavsttas.