Watcyn-Jones, Peter
Penguin books, 1995
Buku Teks
Watcyn-Jones, Peter
Penguin books, 1993
Buku Teks
Nunan, David, author
Pearson Education, 2000
Buku Referensi
Stevick, Earl W.
Abingdon, 1967
Buku Teks
Rinvolucri, Mario, author
Cambridge University Press, 2006
Buku Teks