Submitted on: 20 January 2023.
Revised on: 16 May 2023.
Accepted on: 01 June 2023.
___________________Applied Mathematics Letters---PERGAMON-ELSEVIER SCIENCE LTD
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Submitted on: 26 April 2001.
Revised on: 20 July 2001.
Accepted on: 12 August 2001.
___________________Applied Mathematics Letters---PERGAMON-ELSEVIER SCIENCE LTD
Submitted on: 23 April 2017.
Revised on: 15 July 2017.
Accepted on: 12 August 2017.
___________________Applied Mathematics Letters---PERGAMON-ELSEVIER SCIENCE LTD
Submitted on: 20 October 2010.
Revised on: 22 November 2010.
Accepted on: 22 December 2010.
___________________Applied Mathematics Letters---PERGAMON-ELSEVIER SCIENCE LTD