1. Forrester Research Report. On-Line Internet Spending. 1997.
2. Amazon.com URL: < http://www.amazon.com/ >
3. Firefly Network URL: < http://www.firefly.com/ >
4. PersonaLogic URL: < http://www.personalogic.com/ >
5. R.H. Frank. Microeconomics and Behavior, 3rd ed. McGraw-Hill, Inc., 1996.