Measures on the Closed Subspaces of a Hilbert Space Andrew Gleason Indiana University Mathematics Journal 1957 text pdf 10.1512/iumj.1957.6.56050 10.1512/iumj.1957.6.56050 en Indiana Univ. Math. J. 6 (1957) 885 - 893 state-of-the-art mathematics http://iumj.org/access/