The mathematics of spirograph art(alvesjnr.github.com)
alvesjnr.github.com
The mathematics of spirograph art
http://alvesjnr.github.com/blog/pages/permalinks/how-does-a-spirograph-works2012-Mar-29.html
http://alvesjnr.github.com/blog/pages/permalinks/how-does-a-spirograph-works2012-Mar-29.html