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Submitted on: 16 December 2006.
Revised on: 14 March 2007.
Accepted on: 05 April 2007.
___________________Advances in Applied Mathematics and Mechanics
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Submitted on: 14 November 2005.
Revised on: 10 January 2006.
Accepted on: 03 February 2006.
___________________Advances in Applied Mathematics and Mechanics
Submitted on: 06 April 2004.
Revised on: 21 May 2004.
Accepted on: 17 July 2004.
___________________Advances in Applied Mathematics and Mechanics