http://reply.papertrans.cn/2/133/13273/13273-21.png
Submitted on: 31 January 2002.
Revised on: 26 April 2002.
Accepted on: 10 June 2002.
___________________International Journal of Differential Equations
http://reply.papertrans.cn/2/133/13273/13273-23.png
Submitted on: 09 September 2012.
Revised on: 17 November 2012.
Accepted on: 09 December 2012.
___________________International Journal of Differential Equations
Submitted on: 28 August 2003.
Revised on: 04 December 2003.
Accepted on: 20 December 2003.
___________________International Journal of Differential Equations
Submitted on: 10 December 2004.
Revised on: 18 March 2005.
Accepted on: 06 April 2005.
___________________International Journal of Differential Equations
Submitted on: 14 December 2016.
Revised on: 20 February 2017.
Accepted on: 02 April 2017.
___________________International Journal of Differential Equations
Submitted on: 01 July 2012.
Revised on: 17 October 2012.
Accepted on: 03 November 2012.
___________________International Journal of Differential Equations
http://reply.papertrans.cn/2/133/13273/13273-29.png
Submitted on: 16 March 2014.
Revised on: 19 May 2014.
Accepted on: 09 June 2014.
___________________International Journal of Differential Equations