Hippias: Brief article on this early Sophist, from the Internet Encyclopedia of Philosophy.
Hippias: Wikipedia entry on this ancient polymath, including some material from the 1911 Britannica.
Hippias Biography: Constructed from excerpts from various of Plato's dialogues which mention this Sophist.
Hippias of Elis: Concise scholarly biography of this discoverer of the quadratrix, from the MacTutor History of Mathematics.
Hippias's Quadratrix: Some brief notes on Hippias' attempt to square the circle using this curve, "a pictorial representation of the irrationality of pi."