“…Menaceur et al [29] investigated the bifurcation of limit cycles from the period annulus surrounding the origin of a class of cubic polynomial diferential systems by using the averaging theory of frst order. In the literature of ordinary diferential equations, it is well-known that limit cycles can be yielded by perturbing a system which has a centre in a suitable manner so that limit cycles bifurcate in the perturbed system.…”