Matt May. <a href="http://www.w3.org/TR/2005/NOTE-turingtest-20051123"><cite>Inaccessibility of CAPTCHA.</cite></a> 23 November 2005. W3C Note. URL: <a href="http://www.w3.org/TR/2005/NOTE-turingtest-20051123">http://www.w3.org/TR/2005/NOTE-turingtest-20051123</a>