http://www.cnblogs.com/holbrook/archive/2012/03/21/2409031.html
http://www.cnblogs.com/huxi/archive/2010/06/26/1765808.html
http://www.cnblogs.com/huxi/archive/2010/07/04/1771073.html
http://www.cnblogs.com/huxi/archive/2010/12/05/1897271.html
