On The Existence of Periodic Solutions for a Certain System of Third   Order Nonlinear Differential Equations
  In this paper, we study the existence and uniqueness of periodic solutions of the differential equation of the form   . Here, we obtain some sufficient conditions which guarantee the existence of periodic solutions. This equation is a quite general third- order nonlinear vector differential equation, and one example is given for illustration of the subject. 
Muzaffer Ates
math.CA