Carlton, Eric, author
Routledge & Kegan, 1977
Buku Teks
Thompson, John B., author
Polity Press , 1990
Buku Teks
Seward, Georgene H
McGraw-Hill Book Company Inc, 1946
Buku Teks
Russell, Bertrand, 1872-1970, author
London George Allen & Unwin 1947
Buku Teks
Moore, Wilbert E. (Wilbert Ellis), author
Macmillan, 1955
Buku Teks