Bube, Richard H.
Academic Press, 1981
Buku Teks
Boyer, Ralph E.
St. Paul Minn, 1991
Buku Teks
Waddams, A. Lawrence
The English Language Boook Society and John Murray, , 1968"
Buku Teks
Gray, Alexander
Longmans , 1959
Buku Teks
Clout, hugh D
Pergamon Press, 1977
Buku Teks