Periodic solutions for second-order differential equations with a singular nonlinearity

This paper deals with the existence of positive TT-periodic solutions for the following differential equation ẍ+a(t)x=f(t,x)+c(t), where aa, c∈L1[0,T]c∈L1[0,T] and f∈Car([0,T]×R+,R). The existence results are obtained by using a fixed point theorem in cones.