Convex functions on Grassmannian manifolds and Lawson-Osserman problem
  We derive estimates of the Hessian of two smooth functions defined on Grassmannian manifold. Based on it, we can derive curvature estimates for minimal submanifolds in Euclidean space via Gauss map. In this way, the result for Bernstein type theorem done by Jost and the first author could be improved. 
Y. L. Xin and Ling Yang