Turnock, David
Routledge, 1997
Buku Teks
Lavigne, Marie
Macmillan Press , 1995
Buku Teks
edited by Stephen White, Judy Batt and Paul G. Lewiss
Macmillan, 1993
Buku Teks
edited by Andrew Blasko, Diana Januauskiene
Council for Research in Values and Philosophy, 2008
Buku Teks
McKinnon, Ronald I.
The Johns Hopkins University Press , 1991
Buku Teks