Hammer, Darrel P.
Westview Press, 1990
Buku Teks
Rivoli, Pietra
John Wiley & Sons, 2005
Buku Teks
Beer, Samuel H.
Alfred A. Knopf, 1966
Buku Teks
Wiarda, Howard J.
Hartcourt College Publishers, 2001
Buku Teks
Brzezinski, Zbigniev K.
Frederick A. Praeger, 1962
Buku Teks