Resumen
We establish optimal Lp bounds for the non-tangential maximal function of the gradient of the solution to a second-order elliptic operator in divergence form, possibly non-symmetric, with bounded measurable coefficients independent of the vertical variable, on the domain above a Lipschitz graph in the plane, in terms of the Lp-norm at the boundary of the tangential derivative of the Dirichlet data, or of the Neumann data.