edited by J. Graham Beaumont
Grange Books, 1989
Buku Referensi
Gardner, Howard, author
Basic Books, 1983
Buku Teks
Overstreet, H.A.
W.W Norton & Company, Inc, 1959
Buku Teks
Cairns-Smith, A.G., author
Cambridge University Press, 1996
Buku Teks
Sagan, Carl, author
Presidio Press, 1980
Buku Teks