edited by Jack A. Goldstone, Ted Robert Gurr, Farrokh Moshiri
Westview Press, 1991
Buku Teks
Keylor, William R., 1944-
Oxford University Press, 1996
Buku Teks
Ewen, David
Prentice Hall, 1968
Buku Referensi
Black, C.E.
Alfred A. Knopf, 1961
Buku Teks
Moore, Harry T.
Heinemann, 1976
Buku Teks