Ballard, Robert D., author
National Geographic Society, 1983
Buku Referensi
L`Engle, Madeleine, author
Dell Publishing, 1978
Buku Teks
Sievert, Thomas, author
Spon Press, 2003
Buku Teks
Mumford, Lewis, author
Harcourt, Brace, 1938
Buku Teks
edited by Andrew Blowers, Chris Hammett and Philip Sarre
Hutchinson Educational in association with the Open University Press, 1974
Buku Teks