Mathieson, Alister
Longman, 1995
Buku Teks
Page, Stephen J.
Royutledge, 1995
Buku Teks
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