Allwright, Dick
Cambridge University Press, 1991
Buku Teks
Brown, James Dean
Cambridge University Press, 1988
Buku Teks
McDonough, Jo
Arnold, 1997
Buku Teks
Wisconsin : University of Wirconsin Press
Majalah, Jurnal, Buletin
Hayakawa, S.I.
Harcourt, Brace, 1940
Buku Teks