Laski, Harold J.
George Allen and Unwin, 1960
Buku Teks
McIlroy, John
Manchester University Press , 1995
Buku Teks
Wigham, Eric L.
Oxford University , 1956
Buku Teks
Zweig, F.
Basil Blackwell , 1951
Buku Teks
Barbash, Jack
John Hopkins Press, 1972
Buku Teks