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Submitted on: 13 February 2000.
Revised on: 28 April 2000.
Accepted on: 24 May 2000.
___________________EUROPEAN JOURNAL OF OPERATIONAL RESEARCH
Submitted on: 07 April 2004.
Revised on: 27 July 2004.
Accepted on: 02 September 2004.
___________________EUROPEAN JOURNAL OF OPERATIONAL RESEARCH
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Submitted on: 31 August 1998.
Revised on: 03 December 1998.
Accepted on: 03 January 1999.
___________________EUROPEAN JOURNAL OF OPERATIONAL RESEARCH
Submitted on: 31 July 2005.
Revised on: 27 August 2005.
Accepted on: 28 September 2005.
___________________EUROPEAN JOURNAL OF OPERATIONAL RESEARCH