http://reply.papertrans.cn/3/262/26116/26116-31.png
http://reply.papertrans.cn/3/262/26116/26116-32.png
http://reply.papertrans.cn/3/262/26116/26116-33.png
Submitted on: 23 September 2009.
Revised on: 10 October 2009.
Accepted on: 16 October 2009.
Ratio Juris---UNIV AUTONOMA LATINOAMERICANA UNAULA
http://reply.papertrans.cn/3/262/26116/26116-35.png
http://reply.papertrans.cn/3/262/26116/26116-36.png