Elliot, James
Routledge, 1997
Buku Teks
Longman, 1999
Buku Teks
edited by Tensie Whelan; foreword by Peter A. A. Berle
New York : Uslan Press, 1991,
Buku Referensi
edited by Hooi Den Huan
Prentice-Hall, 1999
Buku Teks
Mathieson, Alister, author
Longman, 1995
Buku Teks