Periodic solutions for a kind of second-order neutral differential systems with deviating arguments (Q1888534)

The authors consider a second-order neutral differential equation of the form \[ \frac{d^2}{dt^2} (x(t) + Cx(t-r)) + \frac{d}{dt}\text{grad}\, F(x(t)) + \text{grad} \,G(x(t-\tau(t))) = p(t). \] Applying a generalized continuation theorem of the coincidence theory, the existence of periodic solutions is established.