An Ergodic Theorem of Abelian Type Luis Baiez-Duarte Indiana University Mathematics Journal 1966 text pdf 10.1512/iumj.1966.15.15039 10.1512/iumj.1966.15.15039 en Indiana Univ. Math. J. 15 (1966) 599 - 607 state-of-the-art mathematics http://iumj.org/access/