Submitted on: 10 October 2002.
Revised on: 24 November 2002.
Accepted on: 06 December 2002.
___________________Acta Mathematicae Applicatae Sinica-English Series
Submitted on: 01 December 2021.
Revised on: 24 February 2022.
Accepted on: 03 April 2022.
___________________Acta Mathematicae Applicatae Sinica-English Series
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Submitted on: 22 July 2007.
Revised on: 06 September 2007.
Accepted on: 07 October 2007.
___________________Acta Mathematicae Applicatae Sinica-English Series
Submitted on: 24 June 2006.
Revised on: 06 October 2006.
Accepted on: 18 November 2006.
___________________Acta Mathematicae Applicatae Sinica-English Series