Gowland, David
Harvester Wheatsheaf, 1991
Buku Teks
Wilson, Thomas
Clarendon Press, 1984
Buku Teks
by Charles C. Holt ... [et al.]
Urban Institute Press, 1971
Buku Teks
Weintraub, Sidney
Addison-Wesley, 1978
Buku Teks
Fishman, Betty G.
Thomas Y. Crowell, 1969
Buku Teks