Watcyn-Jones, Peter
Penguin books, 1995
Buku Teks
Nunan, David
Pearson Education, 2000
Buku Referensi
Stevick, Earl W.
Abingdon, 1967
Buku Teks
Celce-Murcia, Marianne
Cambridge University Press, 2011
Buku Teks
Allwright, Dick
Cambridge University Press, 1991
Buku Teks SO