Vitae philosophorum
Diogenes Laertius
Diogenes Laertius. Hicks, R. D., editor. Cambridge, MA.: Harvard University Press; London: William Heinemann Ltd., 1925.
Others are:
He was the first, so we are told, who introduced the Socratic dialogues as a form of conversation. When Pericles promised to support him and urged him to come to him, his reply was, I will not part with my free speech for money.