Parrot, Martin
Cambridge University Press, 2003
Buku Teks
Protherough, Robert
Open University Press, 1991
Buku Teks
Frieman, Barry B.
McGraw-Hill, 2001
Buku Teks SO
Farrell, Thomas S.C.
Corwin Press, 2006
Buku Teks
Lucas, Michael
Heinemann Educational Books, 1981
Buku Teks