http://www.newscientist.com/article.ns?id=dn2928
http://www.bbc.co.uk/dna/h2g2/A769278
http://plus.maths.org/issue22/news/skimming/index.html
http://en.wikipedia.org/wiki/Stone_skipping
http://www.stoneskimming.co.uk/home.htm
http://news.bbc.co.uk/cbbcnews/hi/sci_tech/newsid_3359000/3359809.stm