edited by Peter Messent and Donald Broom
Grolier International, 1993
Buku Referensi
New York : macmillan Library reference USA, 1997,
Buku Referensi
edited by A. Houghton Brodrick
Frederick A. Praeger, 1972
Buku Teks
Campbell, John R., author
McGraw-Hill , 1969
Buku Teks
by Margaret J. Hartman [and others]
Kendall/Hunt, 1976
Buku Teks