Submitted on: 12 January 2000.
Revised on: 08 February 2000.
Accepted on: 25 February 2000.
___________________International Journal of Applied Nonlinear Science
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Submitted on: 04 July 2005.
Revised on: 02 September 2005.
Accepted on: 29 October 2005.
___________________International Journal of Applied Nonlinear Science
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Submitted on: 27 October 2011.
Revised on: 06 February 2012.
Accepted on: 09 March 2012.
___________________International Journal of Applied Nonlinear Science
Submitted on: 29 March 2012.
Revised on: 02 May 2012.
Accepted on: 07 June 2012.
___________________International Journal of Applied Nonlinear Science
Submitted on: 03 October 2012.
Revised on: 11 December 2012.
Accepted on: 29 January 2013.
___________________International Journal of Applied Nonlinear Science