Submitted on: 17 June 2016.
Revised on: 10 July 2016.
Accepted on: 23 July 2016.
___________________Differential Equations & Applications
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Submitted on: 17 February 2002.
Revised on: 16 June 2002.
Accepted on: 20 July 2002.
___________________Differential Equations & Applications
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Submitted on: 06 January 2015.
Revised on: 30 April 2015.
Accepted on: 20 May 2015.
___________________Differential Equations & Applications
Submitted on: 22 February 2010.
Revised on: 07 April 2010.
Accepted on: 09 May 2010.
___________________Differential Equations & Applications
Submitted on: 11 February 2016.
Revised on: 22 April 2016.
Accepted on: 20 June 2016.
___________________Differential Equations & Applications
Submitted on: 20 December 1998.
Revised on: 06 February 1999.
Accepted on: 24 February 1999.
___________________Differential Equations & Applications