Electronic Journal of Differential Equations,
Vol. 2006(2006), No. 25, pp. 1-8.

Title: On second order periodic boundary-value problems
       with upper and lower solutions in the reversed order
       
Authors: Haiyin Gao (Northeast Normal Univ., Changchun, China)
         Shiyou Weng (Changchun Univ., Jilin, China)
	 Daqing Jiang (Northeast Normal Univ., Changchun, China)
	 Xuezhang Hou (Towson Univ., Baltimore, MD, USA)

Abstract: 
 In this paper, we study the differential equation with the periodic
 boundary value
 $$\displaylines{
 u''(t)=f(t, u(t), u'(t)),\quad t\in [0,  2\pi]\cr
 u(0)=u(2\pi), \quad u'(0)=u'(2\pi).
 }$$
 The existence of solutions to the periodic boundary problem above
 with appropriate conditions is proved by using an upper and lower
 solution method.
 
Submitted November 7, 2005. Published February 28, 2006.
Math Subject Classifications: 34B15, 34B16.
Key Words: Periodic boundary value; existence; upper and lower solutions.