Some Remarks on Axially-Symmetric Potential Theory Albert Heins Indiana University Mathematics Journal 1967 text pdf 10.1512/iumj.1967.16.16014 10.1512/iumj.1967.16.16014 en Indiana Univ. Math. J. 16 (1967) 203 - 212 state-of-the-art mathematics http://iumj.org/access/