1. Theory of Bifurcations of Dynamic Systems on a Plane;Andronov,1973
2. Loss of stability of self-oscillations close to resonance and versal deformations of equivariant vector fields;Arnol'd;Funct. Anal. Appl.,1977
3. The classification of critical points, caustics and wave fronts;Arnol'd,1985
4. J.L.R. Bastos, C.A. Buzzi, J. Torregrosa, Factor reversible systems with applications to planar centers, Preprint, May 2020.
5. On the number of limit cycles which appear with the variation of coefficients from an equilibrium position of focus or center type;Bautin;Am. Math. Soc. Transl.,1954