1) http://me.seu.edu.cn/jmp/jpkc2006/kczd/kc/chap_10/10_6_4.HTM##### 2) http://read.pudn.com/downloads62/doc/project/214377/%E8%AF%AD%E9%9F%B3%E8%AF%86%E5%88%AB/%E8%AF%AD%E9%9F%B3%E5%80%92%E8%B0%B1%E7%89%B9%E5%BE%81%E7%9A%84%E7%A0%94%E7%A9%B6.PDF