“…There are abundant results for weak Hilberts 16th problem restricted to Liénard systems of type ( , ), especially for = − 1, such as types (3, 2) [16], (4, 3) [17], (5,4) [18,19], and (7,6) [20]. More details of the relative researches can be seen in [21][22][23][24][25][26][27][28][29][30][31][32].…”