Boundary Behavior of Non-Parametric Minimal Surfaces Enrico Giusti Indiana University Mathematics Journal 1973 text pdf 10.1512/iumj.1973.22.22039 10.1512/iumj.1973.22.22039 en Indiana Univ. Math. J. 22 (1973) 435 - 444 state-of-the-art mathematics http://iumj.org/access/