Guibernau, Montserrat
Polity Press, 1999
Buku Teks
S. Husin Ali, author
INSAN, 1996
Buku Teks
Marsh, Donald Bailey
Jaques Cattel Press , 1945
Buku Teks
Eppen, Gary D., author
Prentice Hall International, 1988
Buku Teks
Tanham, George K., author
Ferderick A. Praeger, 1966
Buku Teks