1 Smooth solutions of the equation div g ′ |∇u| |∇u| ∇u = 0 are considered generating nonparametric µ-surfaces in R 3 , whenever g is a function of linear growth satisfying in addition ∞ 0 sg ′′ (s)ds < ∞ .Particular examples are µ-elliptic energy densities g with exponent µ > 2 (see [1]) and the minimal surfaces belong to the class of 3surfaces.Generalizing the minimal surface case we prove the closedness of a suitable differential form N ∧dX. As a corollary we find an asymptotic conformal parametrization generated by this differential form.