Electronic Journal of Differential Equations,
Vol. 2006(2006), No. 34, pp. 1-8.

Title: Existence of positive periodic solutions for neutral
       functional differential equations
       
Authors: Zhixiang Li (National Univ. of Defense Technology, China)
         Xiao Wang (National Univ. of Defense Technology, China)

Abstract: 
  We find sufficient conditions for the existence of
  positive periodic solutions of two kinds of neutral 
  differential equations. Using Krasnoselskii's 
  fixed-point theorem in cones, we obtain results that 
  extend and improve previous results. These results are 
  useful mostly when applied to neutral equations with 
  delay in bio-mathematics.
 
Submitted October 25, 2005. Published March 17, 2006.
Math Subject Classifications: 34C25.
Key Words: Positive periodic solution; cone;
  neutral delay differential equation; fixed-point theorem