Weaver, Charles N.
Syarikat First Agency, 1995
Buku Teks
Compton, W. Dale, author
Prentice-Hall, 1997
Buku Teks
Margerison, Charles J.
McGraw-Hill , 1973
Buku Teks
Rohrer
The New American Library, 1969
Buku Teks
Walton, Richard E
Addison-Wesley, 1987
Buku Teks