Clarendon Press Oxford, 1989
Buku Teks
Titmuss, Richard M
Longmans Green and Co, 1950
Buku Teks
Sage Publications, 2002
Buku Teks
Carney, Terry
Oxford University Press Australia, 1991
Buku Teks
Stein, Theodore J., author
Columbia University Press, 2001
Buku Teks