Boundary Regularity for Variational Inequalities R. Jensen Indiana University Mathematics Journal 1980 text pdf 10.1512/iumj.1980.29.29037 10.1512/iumj.1980.29.29037 en Indiana Univ. Math. J. 29 (1980) 495 - 504 state-of-the-art mathematics http://iumj.org/access/