R. Fielding; et al. <a href="http://www.ietf.org/rfc/rfc2616.txt"><cite>Hypertext Transfer Protocol - HTTP/1.1.</cite></a> June 1999. Internet RFC 2616. URL: <a href="http://www.ietf.org/rfc/rfc2616.txt">http://www.ietf.org/rfc/rfc2616.txt</a>