The Multipole Expansion of Radiation Fields A. Calderon Indiana University Mathematics Journal 1954 text pdf 10.1512/iumj.1954.3.53026 10.1512/iumj.1954.3.53026 en Indiana Univ. Math. J. 3 (1954) 523 - 537 state-of-the-art mathematics http://iumj.org/access/