Electronic Journal of Differential Equations,
Vol. 2002(2002), No. 71, pp. 1-13.

Title: Positive periodic solutions of functional
       differential equations and population models

Authors: Daqing Jiang (Northeast Normal Univ., Jilin, China)
         Junjie Wei   (Northeast Normal Univ., Jilin, China)
         Bo Zhang  (Fayetteville State Univ., NC, USA)
         
Abstract: 

 In this paper, we employ Krasnosel'skii's fixed point theorem
  for cones to study the existence of positive periodic solutions
  to a system of infinite delay equations,
  $$  x'(t) = A(t)x(t) + f(t,x_t). $$
  We prove two general theorems and establish new periodicity
  conditions for several  population growth models.
   
Submitted July 5, 2002. Published July 30, 2002.
Math Subject Classifications: 34K13, 92B05.
Key Words: 
Functional differential equations; positive periodic
            solution; population models.