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Submitted on: 04 November 2002.
Revised on: 04 March 2003.
Accepted on: 10 April 2003.
___________________Advances in Pure and Applied Mathematics
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Submitted on: 15 June 1999.
Revised on: 10 August 1999.
Accepted on: 17 September 1999.
___________________Advances in Pure and Applied Mathematics
Submitted on: 21 October 2005.
Revised on: 04 February 2006.
Accepted on: 07 March 2006.
___________________Advances in Pure and Applied Mathematics
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Submitted on: 23 November 2018.
Revised on: 28 January 2019.
Accepted on: 13 February 2019.
___________________Advances in Pure and Applied Mathematics