Kasturi R. Varadarajan Srinivasan Venkatesh Yinyu Ye Jiawei Zhang Approximating the Radii of Point Sets. 1764-1776 2007 36 SIAM J. Comput. 6 http://dx.doi.org/10.1137/050627472 db/journals/siamcomp/siamcomp36.html#VaradarajanVYZ07