Evolution of Nonparametric Surfaces with Speed Depending on Curvature, I. The Gauss Curvature Case. Vladimir Oliker Indiana University Mathematics Journal 1991 text pdf 10.1512/iumj.1991.40.40010 10.1512/iumj.1991.40.40010 en Indiana Univ. Math. J. 40 (1991) 237 - 258 state-of-the-art mathematics http://iumj.org/access/