1. Qualitative Theory of Second Order Dynamical Systems;Andronov,1973
2. Theory of Bifurcations of Dynamical Systems on a Plane;Andronov,1973
3. On the number of limit cycles appearing with variations of the coefficients from an equilibrium state of the type of a focus or a center;Bautin;Mat. Sb. (N.S.),1952
4. Sur la structure des sous-ensembles analytiques réels;Bruhat;C. R. Acad. Sci. Paris,1957
5. Analytical form of differential equations;Brjuno;Trans. Moscow Math. Soc.,1971