Critias
Links
Biography.com: Critias
http://search.biography.com/print_record.pl?id=8199
Very brief biographical information.
Critias
http://www.utm.edu/research/iep/c/critias.htm
Article from the Internet Encyclopedia of Philosophy by William Morison. Notes his life, relationship with Socrates, and various philosophical teachings.
Critias
http://www.in2greece.com/english/historymyth/history/ancient/critias.htm
Biographical article from In2greece.com, focusing on Critias' role in the catastrophic Thirty Tyrants dictatorship of Athens.