Positive periodic solutions for a class of delay differential equations

In this paper, we employ fixed point theorem and functional equation theory to study the existence of positive periodic solutions of the delay differential equationx′(t)=α(t)x(t)-β(t)x2(t)+γ(t)x(t-τ(t))x(t).x′(t)=α(t)x(t)-β(t)x2(t)+γ(t)x(t-τ(t))x(t).Moreover, new explicit conditions for the related population growth models are also given.