On Limit Cycles of Planar Dynamical System Via Dulac- Cherkas Function. Journal of Zankoy Sulaimani - Part A, [S. l.], v. 17, n. 2, p. 45–50, 2015. DOI: 10.17656/jzs.10379. Disponível em: https://jzs.univsul.edu.iq/index.php/jzs/article/view/jzs-10379.. Acesso em: 24 feb. 2024.