Kenneth G. Rehor. <a href="http://www.w3.org/TR/2002/WD-vbi-reqs-20020808"><cite>Voice Browser Interoperation: Requirements.</cite></a> 8 August 2002. W3C Working Draft. (Work in progress.) URL: <a href="http://www.w3.org/TR/2002/WD-vbi-reqs-20020808">http://www.w3.org/TR/2002/WD-vbi-reqs-20020808</a>