Periodic solutions of the third order functional differential equations ✩

We obtain sufficient conditions for the existence of periodic solutions of the following third order nonlinear functional differential equations x (t )+ ax 2k−1(t )+ bx 2k−1(t )+ x2k−1(t )+ g t,x(t − τ1), x (t − τ2) = p(t) = p(t + 2π). Our approach is based on the continuation theorem of the coincidence degree, and the a priori estimate of periodic solutions.  2004 Published by Elsevier Inc