G. Klyne. <a href="http://www.ietf.org/rfc/rfc2533"><cite>A Syntax for Describing Media Feature Sets.</cite></a> March 1999. Internet RFC 2533. URL: <a href="http://www.ietf.org/rfc/rfc2533">http://www.ietf.org/rfc/rfc2533</a>