Some Mixed Boundary Value Problems for Regions with Spherical Boundaries Prem NarainR. Srivastav Indiana University Mathematics Journal 1965 text pdf 10.1512/iumj.1965.14.14040 10.1512/iumj.1965.14.14040 en Indiana Univ. Math. J. 14 (1965) 613 - 627 state-of-the-art mathematics http://iumj.org/access/