A Harnack Inequality Approach to the Interior Regularity of Parabolic Equations Luis CaffarelliLihe Wang Indiana University Mathematics Journal 1993 text pdf 10.1512/iumj.1993.42.42008 10.1512/iumj.1993.42.42008 en Indiana Univ. Math. J. 42 (1993) 159 - 165 state-of-the-art mathematics http://iumj.org/access/