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Submitted on: 06 January 2003.
Revised on: 27 January 2003.
Accepted on: 05 March 2003.
___________________Economics of Transportation---ELSEVIER
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Submitted on: 29 August 2004.
Revised on: 02 October 2004.
Accepted on: 21 October 2004.
___________________Economics of Transportation---ELSEVIER
Submitted on: 14 January 2010.
Revised on: 11 April 2010.
Accepted on: 17 May 2010.
___________________Economics of Transportation---ELSEVIER
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Submitted on: 05 September 2017.
Revised on: 30 September 2017.
Accepted on: 25 October 2017.
___________________Economics of Transportation---ELSEVIER
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