JOHN DAINTITH. "roller ball." A Dictionary of Computing. 2004. Encyclopedia.com. 26 Dec. 2009 <http://www.encyclopedia.com>.
JOHN DAINTITH. "roller ball." A Dictionary of Computing. 2004. Encyclopedia.com. (December 26, 2009). http://www.encyclopedia.com/doc/1O11-rollerball.html
JOHN DAINTITH. "roller ball." A Dictionary of Computing. 2004. Retrieved December 26, 2009 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O11-rollerball.html