Hypoellipticity for infinitely degenerate quasilinear equations and the dirichlet problem

In [10], we considered a class of infinitely degenerate quasilinear equations of the form div $A(x,w)nabla w + overrightarrow r (x,w) cdot nabla w + f(x,w) = 0$ and derived a priori bounds for high order derivatives D ^a w of their solutions in terms of w and ?w. We now show that it is possible to obtain bounds in terms of just w for a further subclass of such equations, and we apply the resulting estimates to prove that continuous weak solutions are necessarily smooth. We also obtain existence, uniqueness, and interior ${varrho ^infty }$ -regularity of solutions for the corresponding Dirichlet problem with continuous boundary data.