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Submitted on: 11 August 2000.
Revised on: 27 October 2000.
Accepted on: 29 November 2000.
___________________COMPUTERS & OPERATIONS RESEARCH
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Submitted on: 03 July 2006.
Revised on: 08 October 2006.
Accepted on: 12 November 2006.
___________________COMPUTERS & OPERATIONS RESEARCH
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Submitted on: 20 June 2000.
Revised on: 26 July 2000.
Accepted on: 21 September 2000.
___________________COMPUTERS & OPERATIONS RESEARCH
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