Jones, J.A.P., author
Longman, 1971
Buku Teks
Mill, John Stuart
A Meridian Book, 1962
Buku Teks
Laski, Harold J., author
George Allen and Unwin, 1948
Buku Teks
Barth, Alan
The Viking Press, 1961
Buku Teks
Newman, Edwin S., author
Oceana Publications,Inc., 1979
Buku Teks