Submitted on: 10 October 2004.
Revised on: 19 October 2004.
Accepted on: 01 November 2004.
NULL
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Submitted on: 23 May 2007.
Revised on: 18 June 2007.
Accepted on: 10 July 2007.
NULL
Submitted on: 20 July 2006.
Revised on: 06 August 2006.
Accepted on: 02 September 2006.
NULL
http://reply.papertrans.cn/3/219/21821/21821-35.png
Submitted on: 14 June 2006.
Revised on: 11 July 2006.
Accepted on: 30 July 2006.
NULL