Collie, Joanne
Cambridge University Press, 1987
Buku Teks
Ur, Penny
Cambridge University Press, 1999
Buku Referensi
edited by Albert H. Marckwardt
National Council of Teachers of English, 1968
Buku Teks SO
Richards, Jack C.
Cambridge University Press, 1985
Buku Teks
Richards, Jack C.
Cambridge University Press, 1994
Buku Teks