${\cal C}^{1,\beta}$ regularity for Dirichlet problems associated to   fully nonlinear degenerate elliptic equations
  In this paper we prove Holder regularity of the gradient for solutions of Dirichlet problem associate to degenerate elliptic equations, extending the recent result of Imbert and Silvestre. Indeed we obtain regularity up to the boundary and when the equation has lower order terms.The proof follows their scheme but requires new tools and new ideas. In particular we give some a priori Lipschitz and H\"older estimates in the presence of boundary condition on one part of the boundary. 
I. Birindelli, F. Demengel
math.AP