Periodic solution for a delay nonlinear population equation with feedback control and periodic external source

In this paper, sufficient conditions are investigated for the existence of periodic (not necessarily pos- itive) solutions for nonlinear several time delay population system with feedback control. nonlinear system affected by an periodic external source is studied. existence of a control variable provides the extension of some previous results obtained in other studies. we give a illustrative example in order to indicate the validity of the assumptions.