Thompson, John B.
Polity Press , 1990
Buku Teks
Seward, Georgene H
McGraw-Hill Book Company Inc, 1946
Buku Teks
Russell, Bertrand, 1872-1970
London George Allen & Unwin 1947
Buku Teks
Moore, Wilbert E. (Wilbert Ellis)
Macmillan, 1955
Buku Teks
Mark Brown, John Pratt, editor
Routledge, 2000
Buku Teks