A Geometric Property of the Two-Dimensional Harmonic Green’s Function Zeev Nehari Indiana University Mathematics Journal 1964 text pdf 10.1512/iumj.1964.13.13057 10.1512/iumj.1964.13.13057 en Indiana Univ. Math. J. 13 (1964) 1009 - 1013 state-of-the-art mathematics http://iumj.org/access/