1.http://wenku.baidu.com/view/386597f37c1cfad6195fa797.html
2.http://wenku.baidu.com/view/4b9521f9f705cc175527094f.html?re=view
3.http://wenku.baidu.com/link?url=idbSvNzz2fLSl1WXiEmtIL1amhQTHmtqqQ6g1cp-oU1X3W4wF2Wdu5LSe745rwjCrM-btR44-we9zLCyMf2ofjjAt2d8wcBT7LFyIHF8Tym
原文：http://www.cnblogs.com/chengqi521/p/6196848.html