Duncan, Colin
John Wiley, 1981
Buku Teks
Beck, John
John Wiley , 1980
Buku Teks
National Council for Civil Liberties with Pluto Press, 1994
Buku Teks
West, E.G.
Institute of Economic Affairs, 1965
Buku Teks
School Government Publishing Co., [date of publication not identified]
Buku Referensi