摘要：This paper deals with the existence of three positive periodic solutions for a class of second order neutral functional differential equations involving the delayed derivative term in nonlinearity $(x(t)-cx(t-\delta)){''}+a(t)g(x(t))x(t)=\lambda b(t)f(t,x(t),x(t-\tau_)(t)),x'(t-\tau_,(t)))$. By utilizing the perturbation method of positive operator and Leggett–Williams fixed point theorem, a group of sufficient conditions are established.
关键词：Neutral functional differential equation;Positive periodic solution;Delayed derivative;Cone;Leggett–Williams fixed point theorem;
