Journal of Inequalities and Applications
Volume 2010 (2010), Article ID 598405, 11 pages
Research Article

Periodic Boundary Value Problems for Second-Order Functional Differential Equations

Department of Mathematics, Hunan University of Science and Technology, Xiangtan, Hunan 411201, China

Received 11 June 2009; Accepted 28 January 2010

Academic Editor: Marta García-Huidobro

Copyright © 2010 Xiangling Fu and Weibing Wang. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


This note considers a periodic boundary value problem for a second-order functional differential equation. We extend the concept of lower and upper solutions and obtain the existence of extreme solutions by using upper and lower solution method.