Φ$(x, u,Du)$ $F(D^2 u) = f(x)$ in $B_1$

for a uniformly elliptic operator $F(·)$ and an appropriate function Φ$(·)$ satisfying minimal
conditions, where ellipticity may degenerate or blow up along the region $\{Du = 0\}$.
http://cvgmt.sns.it/seminar/891/