1. Entertainment Software Association. Historical Sales Figures. (Retrieved February 11, 2003) from http://www.idsa.com/pressroom.html . Now available from http://www.theesa.com/ffbox7.html
2. Interactive Digital Software Association (May 2002), Essential Facts About the Computer and Video Game Industry (Retrieved February 11, 2003) Now available from http://www.theesa.com/IDSABooklet.pdf
3. Pagulayan, R.J., Keeker, K., Wixon, D., Romero, R.L., Fuller, T.: User-centred design in games. In: Jacko, J., Sears, A. (eds.) Handbook for Human-Computer Interaction in Interactive Systems, Lawrence Erlbaum Associates, Inc. (2002)
4. Clanton, C.: An Interpreted Demonstration of Computer Game Design. In: Proceedings of ACM CHI 1998 Conference on Human Factors in Computing Systems: Summary, April 18-23, pp. 1–2 (1998)
5. Lazzaro, N.: Why We Play Games: Four Keys to More Emotion in Player Experiences. In: Proceedings of the Game Developers Conference 2004, March 22-26 (2004)