Cook, Chris
Routledge, 2005
Buku Teks
Palmer, Robert Roswell, 1909-2002
McGraw-Hill, 1992
Buku Teks
edited by John R. Burr
Greenwood Press, 1980
Buku Referensi
McWilliams, Wayne C.
Adamantine Press, 1990
Buku Teks
Stavrianos, Leften Stavros
Prentice-Hall, 1982
Buku Teks