Hippias - Wikipedia entry on this ancient polymath, including some material from the 1911 Britannica. - http://en.wikipedia.org/wiki/Hippias
Hippias's Quadratrix - Some brief notes on Hippias' attempt to square the circle using this curve, "a pictorial representation of the irrationality of pi." - http://www.perseus.tufts.edu/GreekScience/Students/Tim/Quadratrix.html
Hippias of Elis - Concise scholarly biography of this discoverer of the quadratrix, from the MacTutor History of Mathematics. - http://www-groups.dcs.st-and.ac.uk/~history/Mathematicians/Hippias.html