Humphries, James T.
Breton Publishers, 1983
Buku Teks
Humphries, James T.
Delmar Publisher, 1993
Buku Teks
Simpson, Colin D.
Prentice-Hall, 1996
Buku Teks
Kissell, Thomas E.
Prentice Hall International, 1997
Buku Teks
Beach, David P.
Prentice-Hall, 1990
Buku Teks