Submitted on: 02 August 2000.
Revised on: 18 November 2000.
Accepted on: 01 December 2000.
___________________Applied Mathematics Letters---PERGAMON-ELSEVIER SCIENCE LTD
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Submitted on: 19 September 2006.
Revised on: 21 November 2006.
Accepted on: 14 January 2007.
___________________Applied Mathematics Letters---PERGAMON-ELSEVIER SCIENCE LTD
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Submitted on: 24 February 2022.
Revised on: 19 May 2022.
Accepted on: 21 June 2022.
___________________Applied Mathematics Letters---PERGAMON-ELSEVIER SCIENCE LTD
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Submitted on: 03 September 2024.
Revised on: 29 November 2024.
Accepted on: 23 January 2025.
___________________Applied Mathematics Letters---PERGAMON-ELSEVIER SCIENCE LTD
Submitted on: 25 June 2014.
Revised on: 22 October 2014.
Accepted on: 17 December 2014.
___________________Applied Mathematics Letters---PERGAMON-ELSEVIER SCIENCE LTD
Submitted on: 24 April 2006.
Revised on: 25 July 2006.
Accepted on: 09 September 2006.
___________________Applied Mathematics Letters---PERGAMON-ELSEVIER SCIENCE LTD