Inertial manifold for a hyperbolic equation with dissipation

{Sufficient conditions for the existence of an inertial manifold are found for the equation $u_{tt}+2\gamma u_t-\Delta u=f(u, u_t)$, $u=u(x, t), x\in\Omega\Subset\mathbb{R}^N, u|_{\partial\Omega}=0, t>0$ and the function $f$ is supposed to satisfy the Lipschitz condition.