Optimal interior partial regularity for nonlinear elliptic systems with Dini continuous coefficient

In this article, we consider nonlinear elliptic systems of divergence type with Dini continuous coefficients. The authors use a new method introduced by Duzaar and Grotowski, to prove partial regularity for weak solutions, based on a generalization of the technique of harmonic approximation and directly establish the optimal Hölder exponent for the derivative of a weak solution on its regular set.