Submitted on: 18 October 2004.
Revised on: 13 January 2005.
Accepted on: 30 January 2005.
___________________AIMS Mathematics---AMER INST MATHEMATICAL SCIENCES-AIMS
Submitted on: 11 July 2003.
Revised on: 10 September 2003.
Accepted on: 02 October 2003.
___________________AIMS Mathematics---AMER INST MATHEMATICAL SCIENCES-AIMS
Submitted on: 29 August 1999.
Revised on: 23 November 1999.
Accepted on: 12 January 2000.
___________________AIMS Mathematics---AMER INST MATHEMATICAL SCIENCES-AIMS
Submitted on: 10 October 2000.
Revised on: 17 January 2001.
Accepted on: 12 February 2001.
___________________AIMS Mathematics---AMER INST MATHEMATICAL SCIENCES-AIMS
Submitted on: 27 July 2013.
Revised on: 07 October 2013.
Accepted on: 17 October 2013.
___________________AIMS Mathematics---AMER INST MATHEMATICAL SCIENCES-AIMS
Submitted on: 28 January 2025.
Revised on: 02 May 2025.
Accepted on: 18 May 2025.
___________________AIMS Mathematics---AMER INST MATHEMATICAL SCIENCES-AIMS
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Submitted on: 18 August 2011.
Revised on: 02 November 2011.
Accepted on: 17 December 2011.
___________________AIMS Mathematics---AMER INST MATHEMATICAL SCIENCES-AIMS
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