http://www.zhihu.com/question/20054048
http://www.cnblogs.com/luoshupeng/archive/2011/05/01/2033743.html
http://www.cnblogs.com/rockhawk/archive/2010/12/15/1906956.html
http://www.cnblogs.com/luoshupeng/archive/2011/04/27/2030056.html
http://blog.sina.com.cn/s/blog_66a133b70100x44p.html
http://blog.const.net.cn/a/4215.htm
http://blog.sina.com.cn/s/blog_66a133b70100x44p.html
http://blog.csdn.net/jarvischu/article/details/8226938