“…More concretely, in the latter this theory has been employing to obtain the upper bound for the number of zeros of the Melnikov functions, see e.g. [4,7,9,13,15,16,19,20,25,26,30,31,[40][41][42]44] and the references therein. Actually these studies provide lower bounds for the so called weaken Hilbert 16th problem, see e.g.…”