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Submitted on: 20 November 2006.
Revised on: 07 February 2007.
Accepted on: 13 March 2007.
___________________Journal of Geometry and Symmetry in Physics
Submitted on: 02 September 1998.
Revised on: 30 September 1998.
Accepted on: 13 October 1998.
___________________Journal of Geometry and Symmetry in Physics
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Submitted on: 18 March 2012.
Revised on: 07 June 2012.
Accepted on: 06 August 2012.
___________________Journal of Geometry and Symmetry in Physics
Submitted on: 03 March 2011.
Revised on: 27 June 2011.
Accepted on: 08 July 2011.
___________________Journal of Geometry and Symmetry in Physics
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