McCarthy, Michael
Erlangga, 2002
Buku Teks
Bradford, Barbara
Cambridge University Press, 1988
Buku Teks
Barnett, E. de Barry
Longmans Green, 1957
Buku Teks
Hewings, Martin
Cambridge University Press, 2005
Buku Teks
Jones, Leo
Cambridge University Press, 1989
Buku Teks