On Invariant Operator Ranges of the Analytic Toeplitz Operators Eric NordgrenCharles Roy Indiana University Mathematics Journal 1988 text pdf 10.1512/iumj.1988.37.37018 10.1512/iumj.1988.37.37018 en Indiana Univ. Math. J. 37 (1988) 369 - 377 state-of-the-art mathematics http://iumj.org/access/