http://wenku.baidu.com/view/d54e0cec81c758f5f61f67a4.html
http://wenku.baidu.com/view/edc94d2acfc789eb172dc8cf.html
http://blog.csdn.net/leeli1987/article/details/6633769
http://wenku.baidu.com/view/d54e0cec81c758f5f61f67a4.html
http://wenku.baidu.com/view/edc94d2acfc789eb172dc8cf.html
http://blog.csdn.net/leeli1987/article/details/6633769