1. Virtual Reality and its application in China—an overview;Zhigeng;The International Journal of Virtual Reality,2000
2. Virtual reality;Jiaoying,2002
3. Elf Bowling Game. http://www.freechristmasavers.com/elfbowling.htm
4. Hough PVC. A method and means for recognizing complex patterns. US Pattern, 1962.
5. Collision detection and response for computer animation, proc SIGGRAPH ’88;Moore;Computer Graphics,,1988