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Submitted on: 27 October 2001.
Revised on: 20 January 2002.
Accepted on: 05 February 2002.
___________________DISCRETE APPLIED MATHEMATICS---ELSEVIER
Submitted on: 28 August 2000.
Revised on: 07 October 2000.
Accepted on: 11 November 2000.
___________________DISCRETE APPLIED MATHEMATICS---ELSEVIER
Submitted on: 05 June 2002.
Revised on: 06 September 2002.
Accepted on: 20 September 2002.
___________________DISCRETE APPLIED MATHEMATICS---ELSEVIER
Submitted on: 08 December 2019.
Revised on: 30 March 2020.
Accepted on: 02 May 2020.
___________________DISCRETE APPLIED MATHEMATICS---ELSEVIER
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http://reply.papertrans.cn/1/76/7542/7542-17.png
Submitted on: 02 January 1999.
Revised on: 25 February 1999.
Accepted on: 24 April 1999.
___________________DISCRETE APPLIED MATHEMATICS---ELSEVIER
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Submitted on: 18 July 2011.
Revised on: 31 October 2011.
Accepted on: 24 December 2011.
___________________DISCRETE APPLIED MATHEMATICS---ELSEVIER