Upper Semi-Continuity and the Monge-Ampere Differential Inequality Victor Shapiro Indiana University Mathematics Journal 1980 text pdf 10.1512/iumj.1980.29.29035 10.1512/iumj.1980.29.29035 en Indiana Univ. Math. J. 29 (1980) 467 - 477 state-of-the-art mathematics http://iumj.org/access/