Kotler, Philip (2003).Marketing Insights From A to Z: 80 Concepts Every Manager Needs To Know. Hoboken, NJ: John Wiley & Sons, Inc. 
Rifkin, Jeremy (2000). The Age of Access: 
The New Culture of Hypercapitalism Where All of Life is a Paid-For Experience. New York, NY: Jeremy P. Tarcher/Putman and Penguin