Complexity of the classical kernel functions of potential theory Steven Bell Bergman kernelSzego kernelGreen's functionPoisson kernel Indiana University Mathematics Journal 1995 text pdf 10.1512/iumj.1995.44.2030 10.1512/iumj.1995.44.2030 en Indiana Univ. Math. J. 44 (1995) 1337 - 1369 state-of-the-art mathematics http://iumj.org/access/