http://www.cnblogs.com/hkncd/archive/2012/03/23/2413917.html
http://www.cnblogs.com/huc87/archive/2009/04/05/1429777.html
http://www.cnblogs.com/JimmyZhang/archive/2007/09/04/880967.html
http://www.cnblogs.com/cmt/archive/2013/06/01/3112725.html
原文：http://www.cnblogs.com/cn-chenhao/p/4767034.html