Kissell, Thomas E.
Prentice Hall International, 1997
Buku Teks
McCormick, Ernest James
Prentice-Hall, 1980
Buku Teks
Toynbee, Arnold J.
The Beacon Press , 1961
Buku Teks
Forrester, Jay Wright
John Wiley & Sons, 1961
Buku Teks
McCormick, Ernest James
Prentice-Hall, 1984
Buku Teks