Ur, Penny, author
Cambridge University Press, 1999
Buku Referensi
Ur, Penny, author
Cambridge University Press, 2006
Buku Teks
Richards, Jack C., author
Cambridge University Press, 2006
Buku Teks
Richards, Jack C., author
Cambridge University Press, 1994
Buku Teks
Richards, Jack C., author
Cambridge University Press, 1985
Buku Teks