Pincas, Anita
Macmillan Press, 1983
Buku Teks
Hewings, Martin, author
Cambridge University Press, 2005
Buku Teks
Hill, LA
Oxford University press, 1982
Buku Teks
McCullagh, Marie, author
Cambridge university press, 2008
Buku Teks
Comfort, Jeremy, author
Oxford University Press, 1994
Buku Teks