Asimov, Isaac, author
Greenwood Press , 1979
Buku Teks
Ihde, Aaron John
Dover Publications, 1984
Buku Referensi
Stillman, John Maxson
Dover Publications, 1960
Buku Teks
Asimov, Isaac, author
Grafton Books, 1990.
Buku Teks
Asimov, Isaac, author
Collier Books, 1962
Buku Teks