R-Operators II. On the Approximation of Certain Operator-Valued Analytic Functions and the Hermitian Moment Problem F. Narcowich Indiana University Mathematics Journal 1977 text pdf 10.1512/iumj.1977.26.26038 10.1512/iumj.1977.26.26038 en Indiana Univ. Math. J. 26 (1977) 483 - 513 state-of-the-art mathematics http://iumj.org/access/