Weinberg, Roy David
Oceana, 1979
Buku Teks
Isaacs, Stephen L., author
Human Science Press, 1981
Buku Teks
Daniel J. Lathrope, editor
West Group, 2003
Buku Teks
Miller, Edwin L., author
John Wiley & Sons, 2008
Buku Teks
Commonwealth Secretariat, 1977
Buku Teks