Johan Hjelm; Jim Pitkow; Henrik Frystyk Nielsen. <a href="http://www.w3.org/TR/1999/NOTE-WCA-19990319"><cite>Web Characterization: From working group to activity.</cite></a> 19 March 1999. W3C Note. URL: <a href="http://www.w3.org/TR/1999/NOTE-WCA-19990319">http://www.w3.org/TR/1999/NOTE-WCA-19990319</a>