1、http://blog.csdn.net/letmefish/article/details/51839080
2、http://www.jb51.net/article/67314.htm
3、https://wenku.baidu.com/view/80ec0a6c1eb91a37f1115cab.html
4、http://www.cnblogs.com/xh6300/p/5915717.html
