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Submitted on: 22 December 2014.
Revised on: 18 January 2015.
Accepted on: 28 January 2015.
TRANSPORTATION RESEARCH PART D-TRANSPORT AND ENVIRONMENT
Submitted on: 02 January 1999.
Revised on: 22 January 1999.
Accepted on: 11 February 1999.
TRANSPORTATION RESEARCH PART D-TRANSPORT AND ENVIRONMENT
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