“…Concerning regular points, let us mention slightly more precise results on the regularity of the free boundary when the modulus of continuity is not only controled at the origin 0, but controled at any points (see Blank [5] for sharp results). See the previous works of Caffarelli [6,7,8,9], Weiss [38], and Caffarelli, Karp, Shahgholian [13] for Lipschitz coefficients, and also the work of Caffarelli, Kinderlehrer [14] for some related estimates on the modulus of continuity of the solution or of its gradient.…”