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Submitted on: 28 June 1999.
Revised on: 12 October 1999.
Accepted on: 14 November 1999.
___________________International Journal of Differential Equations
Submitted on: 30 July 1998.
Revised on: 14 October 1998.
Accepted on: 07 November 1998.
___________________International Journal of Differential Equations
Submitted on: 19 April 2022.
Revised on: 13 August 2022.
Accepted on: 13 September 2022.
___________________International Journal of Differential Equations
Submitted on: 08 April 2018.
Revised on: 11 July 2018.
Accepted on: 05 August 2018.
___________________International Journal of Differential Equations
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Submitted on: 02 November 2009.
Revised on: 12 February 2010.
Accepted on: 01 April 2010.
___________________International Journal of Differential Equations
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Submitted on: 30 September 2007.
Revised on: 15 December 2007.
Accepted on: 18 January 2008.
___________________International Journal of Differential Equations