Equivalence of Homogeneous Principal Hardy Submodules Keren Yan Indiana University Mathematics Journal 1992 text pdf 10.1512/iumj.1992.41.41048 10.1512/iumj.1992.41.41048 en Indiana Univ. Math. J. 41 (1992) 875 - 884 state-of-the-art mathematics http://iumj.org/access/