Almost periodic solutions of forced vectorial Liénard equations

We describe the set of bounded or almost periodic solutions of the following Liénard system: u″+ddt[∇F(u)]+Cu=e(t), where e:R⟶RN is almost periodic, C:RN⟶RN is a symmetric and nonsingular linear operator, and ∇F denotes the gradient of the convex function F on RN. Then, we state a result of existence and uniqueness of almost periodic solution.