Submitted on: 29 December 2001.
Revised on: 07 February 2002.
Accepted on: 21 February 2002.
NULL
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http://reply.papertrans.cn/3/226/22505/22505-33.png
Submitted on: 12 December 2008.
Revised on: 18 January 2009.
Accepted on: 05 February 2009.
NULL
http://reply.papertrans.cn/3/226/22505/22505-35.png
Submitted on: 20 October 2006.
Revised on: 30 November 2006.
Accepted on: 17 December 2006.
NULL