or Kalman conjectures are fulfilled, there are no periodic solutions by describing function method, but counterexamples with hidden periodic attractors are known. Counterexamples to the describing function method can be constructed for discontinuous dynamical systems when a rest segment destroys predicted limit cycles. Therefore, the application of the describing function method requires additional justification. References Further reading N. Krylov and N. Bogolyubov: Introduction to Nonlinear Mechanics, Princeton University Press, 1947 A. Gelb and W. E. Vander Velde: Multiple-Input Describing Functions and Nonlinear System Design, McGraw Hill, 1968. James K. Roberge, Operational Amplifiers: Theory and Practice, chapter 6: Non-Linear Systems, 1975; free copy courtesy of MIT OpenCourseWare 6.010 (2013); see also (1985) video recording of Roberge's lecture on describing functions P.W.J.M. Nuij, O.H. Bosgra, M. Steinbuch, Higher Order Sinusoidal Input Describing Functions for the Analysis of Nonlinear Systems with Harmonic Responses, Mechanical Systems and Signal Processing, 20(8), 1883–1904, (2006) External links Electrical Engineering Encyclopedia: Describing Functions Nonlinear control Hidden oscillation