On Some Extremal Positive Definite Functions A. GarsiaE. RodemichH. Rumsey Indiana University Mathematics Journal 1969 text pdf 10.1512/iumj.1969.18.18060 10.1512/iumj.1969.18.18060 en Indiana Univ. Math. J. 18 (1969) 805 - 834 state-of-the-art mathematics http://iumj.org/access/