Extensions of Matrix Valued Functions and Block Matrices Harry DymI. Gohberg Indiana University Mathematics Journal 1982 text pdf 10.1512/iumj.1982.31.31052 10.1512/iumj.1982.31.31052 en Indiana Univ. Math. J. 31 (1982) 733 - 765 state-of-the-art mathematics http://iumj.org/access/