Spherical Means in Harmonic Spaces B. Fusaro Indiana University Mathematics Journal 1969 text pdf 10.1512/iumj.1969.18.18047 10.1512/iumj.1969.18.18047 en Indiana Univ. Math. J. 18 (1969) 603 - 606 state-of-the-art mathematics http://iumj.org/access/