The Commutant of an Analytic Toeplitz Operator, II C. Cowen Indiana University Mathematics Journal 1980 text pdf 10.1512/iumj.1980.29.29001 10.1512/iumj.1980.29.29001 en Indiana Univ. Math. J. 29 (1980) 1 - 12 state-of-the-art mathematics http://iumj.org/access/