Cassinelli, C.W.
University of Washington Press , 1961
Buku Teks
Simon, Yves R.
The University of Chicago Press, 1951
Buku Teks
MacIver, Robert M.
Oxford, 1926
Buku Teks
Laski, Harold J.
George Allen and Unwin, 1948
Buku Teks
Laski, Harold J.
Penguin Books, 1937
Buku Teks