Sufficient conditions for the existence of at least n or exactly n limit cycles for the Lienard differential systems

In this paper we study the limit cycles of the Lienard differential system of the form x + f(x)(x) over dot + g(x) = 0, or its equivalent system (x) over dot = y - F(x), (y) over dot = -g(x). We provide sufficient conditions in order that the system exhibits at least n or exactly n limit cycles. (C) 2007 Elsevier Inc. All rights reserved.MathematicsSCI(E)0ARTICLE111-2324