1. A.A. Andronov, A.A. Vitt, and S.E. Haykin, Teoriya Kolebaniy, Nauka, Moskva., pp. 568, 1981.
2. I. Gerard and J. Daniel, Elementary Stability and BIfurcation Theory, Springer Verlag, 1980.
3. J. Guckenheimer and Ph. Holmes, Nonlinear Oscillations, Dynamical Systems, and Bifurcations of Fields, Springer-Verlag, pp. 461, 1983.
4. A. Yu Mitropolyskiy, Problemi Asimptoticheskoy Teorii Nestashionarnih Kolebaniy, Nauka Moskva, pp. 431, 1964.
5. K. Hedrih (Stevanović), “Trigger of coupled singularities” (invited plenary lecture), Dynamical Systems — Theory and Applications, Edited By J. Awrejcewicz and all, Lodz, pp. 51–78, 2001.