http://blog.csdn.net/zdw890412/article/details/7386314 //有点乱
http://www.cnblogs.com/fanchangfa/archive/2012/08/25/2657012.html
http://www.2cto.com/kf/201403/284469.html //不错
http://blog.csdn.net/chonbj/article/details/11804153 //通俗
http://www.360doc.com/content/13/0507/19/12229927_283691996.shtml
http://www.cnblogs.com/allenzheng/archive/2013/04/28/3050065.html