Boundary Regularity for Elliptic Problems with Continuous Coefficients

We consider weak solutions of second order nonlinear elliptic systems in divergence form or of quasi-convex variational integrals with continuous coefficients under superquadratic growth conditions. Via the method of $\mathcal{A}$-harmonic approximation we give a characterization of regular boundary points using and extending some new techniques recently developed by M. Foss and G. Mingione [Ann. Inst. Henri Poincaré Anal. Non Linéaire 25 (2008) 471–503]