Submitted on: 31 January 2009.
Revised on: 26 February 2009.
Accepted on: 26 April 2009.
___________________International Transactions in Operational Research
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Submitted on: 31 March 2015.
Revised on: 17 June 2015.
Accepted on: 15 August 2015.
___________________International Transactions in Operational Research
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Submitted on: 12 April 2014.
Revised on: 24 June 2014.
Accepted on: 24 July 2014.
___________________International Transactions in Operational Research
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Submitted on: 08 September 2010.
Revised on: 28 October 2010.
Accepted on: 12 December 2010.
___________________International Transactions in Operational Research
Submitted on: 18 July 2000.
Revised on: 04 September 2000.
Accepted on: 28 October 2000.
___________________International Transactions in Operational Research
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