Butterfield, Herbert
Free Press, 1957
Buku Teks SO
Tate, C. Neal
New York University press, 1995
Buku Teks
Ross, Robert
Polity Press, 2008
Buku Teks
by Leften S. Stavrianos ... [and others]
Allyn and Bacon, 1966
Buku Teks SO
Ching, Francis D.K., 1943-
John Wiley & Sons, 2011
Buku Teks SO