Reference for “Inaccessibility of CAPTCHA”

@TechReport{May:05:IC,
  author      = "Matt May",
  title       = "Inaccessibility of {CAPTCHA}",
  month       = nov,
  note        = "http://www.w3.org/TR/2005/NOTE-turingtest-20051123/",
  year        = "2005",
  bibsource   = "http://w2.syronex.com/jmr/w3c-biblio",
  type        = "{W3C} Note",
  institution = "W3C",
}