Asimov, I. (1989). Frontiers: New discoveries about man and his planet, outer space, and the universe. Plume.
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रAsimov, Isaac. Frontiers: New Discoveries About Man and His Planet, Outer Space, and the Universe. New York: Plume, 1989.
एमएलए (9वां संस्करण) प्रशस्ति पत्रAsimov, Isaac. Frontiers: New Discoveries About Man and His Planet, Outer Space, and the Universe. Plume, 1989.
चेतावनी: ये उद्धरण हमेशा 100% सटीक नहीं हो सकते हैं.