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Submitted on: 12 January 2002.
Revised on: 01 April 2002.
Accepted on: 28 May 2002.
___________________Journal of Mathematics in Industry
Submitted on: 28 December 2014.
Revised on: 13 March 2015.
Accepted on: 23 March 2015.
___________________Journal of Mathematics in Industry
Submitted on: 29 October 2005.
Revised on: 29 December 2005.
Accepted on: 25 January 2006.
___________________Journal of Mathematics in Industry
Submitted on: 19 July 2010.
Revised on: 13 November 2010.
Accepted on: 11 December 2010.
___________________Journal of Mathematics in Industry
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