Reduction Theory of Operators on Hilbert Space - The Invariant Subspace Problem- Noboru Suzuki Indiana University Mathematics Journal 1971 text pdf 10.1512/iumj.1971.20.20089 10.1512/iumj.1971.20.20089 en Indiana Univ. Math. J. 20 (1971) 953 - 958 state-of-the-art mathematics http://iumj.org/access/