Convergence of Solutions of Parabolic Equations to a Steady State Avner Friedman Indiana University Mathematics Journal 1959 text pdf 10.1512/iumj.1959.8.58004 10.1512/iumj.1959.8.58004 en Indiana Univ. Math. J. 8 (1959) 57 - 76 state-of-the-art mathematics http://iumj.org/access/