A Functional Calculus for Several Commuting Operators A. McIntoshAlan Pryde Indiana University Mathematics Journal 1987 text pdf 10.1512/iumj.1987.36.36024 10.1512/iumj.1987.36.36024 en Indiana Univ. Math. J. 36 (1987) 421 - 439 state-of-the-art mathematics http://iumj.org/access/