“…When F (x, y) and G(x, y) are polynomials of degrees 2, limit cycles can occur and there is an extensive literature dealing with their existence, number and stability (see for instance May [13], Lloyd, Pearson,Saèz and Szántó [11,12], Huang [8], Huang, Wang, Cheng [9], Huang, Zhu [10], Boqian and Demeng [4], Cheng [5], and references therein), but to our knowledge, the exact analytic expressions of the limit cycles for a given kolmogorov system is still unknown except in simplest and specific cases.…”