The Mycielski-Paszkowski Diffusion Problem R. Redheffer Indiana University Mathematics Journal 1960 text pdf 10.1512/iumj.1960.9.59035 10.1512/iumj.1960.9.59035 en Indiana Univ. Math. J. 9 (1960) 607 - 621 state-of-the-art mathematics http://iumj.org/access/