Heidensohn, Frances
Macmillan, 1989
Buku Teks
Mike Fitzgerald, Gregor McLennan and Jennie Pawson at the Open University.
Routledge in association with Open University Press, 2001
Buku Teks
Windlesham, Lord
Clarendon Press, 1996
Buku Teks
McAllister, David
Avebury, 1992
Buku Teks
Brownlee, Ian
Longman, 1998
Buku Teks