1. Playful learning in the twenty-first century: Motivational variables, interest assessment, and games
2. Serious games: Games that educate, train, and inform;michael;Muska and Lipman/Premier-Trade,2005
3. From Visual Simulation to Virtual Reality to Games;zyda;Computer,2005
4. Harnessing the Power of Games in Education;squire;Insight,2003