Xiaoping Yuan A variant of KAM theorem with applications to nonlinear wave equations of higher dimension (489K, AMS-TeX) ABSTRACT. The existence of lower dimensional KAM tori is shown for a class of nearly integrable Hamiltonian systems where the second Melnikov's conditions are relaxed, at the cost of the stronger regularity of the perturbed nonlinear term. As a consequence, it is proved that there exist many linearly stable invariant tori and thus quasi-periodic solutions for nonlinear wave equations of non-local nonlinearity and of higher spatial dimension.