Submitted on: 09 April 2009.
Revised on: 26 May 2009.
Accepted on: 08 July 2009.
___________________International Journal of Differential Equations
http://reply.papertrans.cn/2/133/13273/13273-32.png
Submitted on: 30 December 2009.
Revised on: 08 March 2010.
Accepted on: 03 April 2010.
___________________International Journal of Differential Equations
Submitted on: 22 July 2008.
Revised on: 25 September 2008.
Accepted on: 25 October 2008.
___________________International Journal of Differential Equations
Submitted on: 26 July 2009.
Revised on: 12 November 2009.
Accepted on: 30 November 2009.
___________________International Journal of Differential Equations
Submitted on: 19 May 2000.
Revised on: 24 August 2000.
Accepted on: 11 October 2000.
___________________International Journal of Differential Equations