Infinite Dimensional Versions of a Theorem of Brickman-Fillmore R. DouglasC. Foiacs Indiana University Mathematics Journal 1976 text pdf 10.1512/iumj.1976.25.25027 10.1512/iumj.1976.25.25027 en Indiana Univ. Math. J. 25 (1976) 315 - 320 state-of-the-art mathematics http://iumj.org/access/