Collis, David J., author
McGraw-Hill Irwin, 2005
Buku Teks
Schlosser, Michel, author
Prentice-Hall, 1989
Buku Teks
Hardin, Russell
Oxford University Press, 1999
Buku Teks
Graber, Mark A., author
Oxford University Press, 2015
Buku Teks
Friedrich, Carl J., author
Boston University Press, 1967
Buku Teks