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
May, James R, author
Cambridge University Press, 2014
eBooks
Barrow, John D., author
Oxford University Press , 1998
Buku Teks