On a Variational Problem with Inequalities on the Boundary H. Lewy Indiana University Mathematics Journal 1968 text pdf 10.1512/iumj.1968.17.17054 10.1512/iumj.1968.17.17054 en Indiana Univ. Math. J. 17 (1968) 861 - 884 state-of-the-art mathematics http://iumj.org/access/