Operator Algebras with Complemented Invariant Subspace Lattices T. Hoover Indiana University Mathematics Journal 1973 text pdf 10.1512/iumj.1973.22.22086 10.1512/iumj.1973.22.22086 en Indiana Univ. Math. J. 22 (1973) 1029 - 1035 state-of-the-art mathematics http://iumj.org/access/