Freeborn, Dennis, author
Macmillan, 1993
Buku Teks
Johnston, Trevor, author
Cambridge University Press, 2014
Buku Teks
Allwright, Dick, author
Cambridge University Press, 1991
Buku Teks
Holt, Rinehart and Winston, 1990
Buku Teks
Lee, Irving J., author
Harper & Brothers, 1941
Buku Teks