“…A limit cycle of system (1.1) is an isolated periodic solution in the set of all periodic solutions of system (1.1). If a limit cycle is contained in the zero level set of a polynomial function, see for example, [ [1], [4], [5], [9], [11]], then we say that it is algebraic, otherwise it is called non-algebraic see for example ([2], [4], [8], [10]). The topic of limit cycles is interesting both in mathematics and in science and many models from physics, engineering, chemistry, biology, economics,..., were displayed as differential systems with limit cycles.…”