1. On the number of limit cycles which appear with the variation of coefficients from an equilibrium position of focus or center type;Bautin;Mat. Sb.,1952
2. Local Theory of Nonlinear Analytic Ordinary Differential Equations;Bibikov,1979
3. Analytic form of differential equations;Bruno;Trans. Moscow Math. Soc.,1971
4. Normalizable, integrable and linearizable saddle points in the Lotka–Volterra system;Christopher;Qual. Theory Dyn. Syst.,2004
5. On the singular points of polynomial systems;Dong,2013