Existence of positive periodic solutions for a neutral Liénard equation with a singularity of repulsive type

Existence of positive periodic solutions for super-linear neutral Liénard equation with a singularity of attractive type

“…After the pioneering paper [6] came out, many scholars put their attention to the periodic problems of second order singular differential equations without friction term (see [7][8][9][10][11][12][13] and the references therein). Beginning with the paper of Habets-Sanchez in [14], the interest in the problem of periodic solution for second order singular differential equations with friction term has increased [15][16][17][18][19][20][21]. Hakl, Torres, and Zamora considered the periodic problem for the singular equation of attractive type…”