http://blog.csdn.net/wang122188/article/details/7699032
http://www.cnblogs.com/qixue/p/3928775.html
http://blog.csdn.net/dongtianlaile/article/details/9854263
http://blog.sina.com.cn/s/blog_68f262210101mcxp.html
原文：http://my.oschina.net/u/855532/blog/379827