On the Non-Solvability of Dirichlet's Problem for the Minimal Surface Equation Joachim Nitsche Indiana University Mathematics Journal 1965 text pdf 10.1512/iumj.1965.14.14050 10.1512/iumj.1965.14.14050 en Indiana Univ. Math. J. 14 (1965) 779 - 788 state-of-the-art mathematics http://iumj.org/access/