Ross, Janet
Harper & Row , 1965
Buku Teks
Hyland, Ken
Cambridge University Press, 2007
Buku Teks
Barbara Kroll, editor
Cambridge University Press, 2003
Buku Teks
Lugton, Robert C.
Prentice-Hall, 1978
Buku Teks
edited by Ken Hyland, Fiona Hyland
Cambridge University Press , 2006
Buku Teks