Ian Jacobs; David Raggett; Arnaud Le Hors. <a href="http://www.w3.org/TR/1998/REC-html40-19980424"><cite>HTML 4.0 Specification.</cite></a> 24 April 1998. W3C Recommendation. URL: <a href="http://www.w3.org/TR/1998/REC-html40-19980424">http://www.w3.org/TR/1998/REC-html40-19980424</a>