On periodic solutions of second-order differential equations with attractive–repulsive singularities

Sufficient conditions for the existence of a solution to the problemu″(t)=g(t)uμ(t)−h(t)uλ(t)+f(t)for a.e.t∈[0,ω],u(0)=u(ω),u′(0)=u′(ω) are established.