S. Nocilla et P. Moroni, EXISTENCE AND NONEXISTENCE OF PERIODIC-SOLUTIONS FOR THE LIENARD AND RELATED EQUATIONS, Nonlinear dynamics, 6(3), 1994, pp. 331-352
The existence of periodic solutions of Lienard type equations is conve
rted into the existence of special fixed point problems with auxiliary
conditions. A general method for exact calculation of the limit cycle
s is given, and the corresponding numerical iterative procedure is car
ried out in significant cases, with comparison to standard Runge-Kutta
numerical integration. On the basis of the general theory, criteria f
or the existence of limit cycles are given and tested in particular ca
ses.