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Submitted on: 12 March 2005.
Revised on: 22 April 2005.
Accepted on: 12 June 2005.
___________________Advances in Applied Mathematics and Mechanics
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Submitted on: 05 June 2011.
Revised on: 17 September 2011.
Accepted on: 08 November 2011.
___________________Advances in Applied Mathematics and Mechanics
Submitted on: 25 June 2006.
Revised on: 06 August 2006.
Accepted on: 08 September 2006.
___________________Advances in Applied Mathematics and Mechanics
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