1. Uniqueness of limit cycles for complex differential equations with two monomials;M J �lvarez;J. Math. Anal. Appl,2023
2. On the number of limit cycles appearing with variation of the coefficients from an equilibrium state of the type of a focus or a center;N N Bautin;Russian. American Math. Soc. Translation,1952
3. The relative position and number of limit cycles of the quadratic differential system;L Chen;Acta Math. Sin,1979
4. Limit Cycles of Differential Equations