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Submitted on: 19 December 2001.
Revised on: 11 February 2002.
Accepted on: 16 March 2002.
___________________Bulletin of Mathematical Analysis and Applications
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Submitted on: 25 April 2011.
Revised on: 16 June 2011.
Accepted on: 23 July 2011.
___________________Bulletin of Mathematical Analysis and Applications
Submitted on: 03 September 2023.
Revised on: 28 October 2023.
Accepted on: 22 December 2023.
___________________Bulletin of Mathematical Analysis and Applications
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Submitted on: 25 October 2008.
Revised on: 11 December 2008.
Accepted on: 17 January 2009.
___________________Bulletin of Mathematical Analysis and Applications
Submitted on: 25 April 2007.
Revised on: 15 May 2007.
Accepted on: 05 June 2007.
___________________Bulletin of Mathematical Analysis and Applications
Submitted on: 15 April 2010.
Revised on: 25 July 2010.
Accepted on: 15 August 2010.
___________________Bulletin of Mathematical Analysis and Applications