Mean value inequalities Ping LiJenn-Nan Wang Indiana University Mathematics Journal 1999 text pdf 10.1512/iumj.1999.48.1714 10.1512/iumj.1999.48.1714 en Indiana Univ. Math. J. 48 (1999) 1257 - 1284 state-of-the-art mathematics http://iumj.org/access/