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Submitted on: 14 April 2013.
Revised on: 19 May 2013.
Accepted on: 15 July 2013.
___________________INTERNATIONAL JOURNAL OF PRODUCTION ECONOMICS
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Submitted on: 27 March 2002.
Revised on: 16 July 2002.
Accepted on: 07 September 2002.
___________________INTERNATIONAL JOURNAL OF PRODUCTION ECONOMICS