We perturb the differential system , , and for inside the class of all polynomial differential systems of degree in , and we prove that at most limit cycles can be obtained for the perturbed system using the first-order averaging theory.
Zouhair Diab. Amar Makhlouf. "Limit Cycles for the Class of -Dimensional Polynomial Differential Systems." J. Appl. Math. 2016 1 - 5, 2016. https://doi.org/10.1155/2016/1868027