On a Coerciveness Theorem by Schulenberger and Wilcox Tosio Kato Indiana University Mathematics Journal 1975 text pdf 10.1512/iumj.1975.24.24082 10.1512/iumj.1975.24.24082 en Indiana Univ. Math. J. 24 (1975) 979 - 985 state-of-the-art mathematics http://iumj.org/access/