Cassell, Douglas A.
Reston Publishing, 1983
Buku Teks
Bolton, William, 1933-
Nwenes, 1994
Buku Teks
Masters, Gilbert M.
Prentice-Hall, 2008
Buku Teks
Callister, William D., Jr., 1940-
John Wiley & Sons, 2000
Buku Teks
Morley, Arthur
English Language Book Society, 1962
Buku Teks