George, Stephen
Oxford University Press, 1985
Buku Teks
edited by Stephen White, Judy Batt and Paul G. Lewiss
Macmillan, 1993
Buku Teks
Nugent, Neill
Macmillan, 1994
Buku Teks
Wiarda, Howard J.
Hartcourt College Publishers, 2001
Buku Teks
by Christopher S. Allen [and others]
D.C. Health, 1987
Buku Teks