Electronic Journal of Differential Equations,
Vol. 2008(2008), No. 38, pp. 1-8.

Title: Positive periodic solutions of neutral functional
       differential equations with a parameter and impulse
 
Authors: Xuanlong Fan (Yunnan Univ., Kunming, Yunnan, China)
         Yongkun Li   (Yunnan Univ., Kunming, Yunnan, China)

Abstract: 
 In this paper, we consider first-order neutral differential
 equations with a parameter and impulse in the form of
 $$\displaylines{
 \frac{d}{dt}[x(t)-c x(t-\gamma)]=-a(t)g(x(h_1(t)))x(t)+\lambda
 b(t) f\big(x(h_2(t))\big),\quad t\neq t_j;\cr
 \Delta \big[x(t)-c x(t-\gamma)\big]=I_j\big(x(t)\big),\quad
 t=t_j,\; j\in\mathbb{Z}^+.
 }$$
 Leggett-Williams fixed point
 theorem, we prove the existence of three positive periodic solutions.
 
Submitted December 16, 2007. Published March 14, 2008.
Math Subject Classifications: 34K13, 34K40.
Key Words: Periodic solution; functional differential equation;
           fixed point; cone.