Kevin Smith; Andrea Perego; Phil Archer. <a href="http://www.w3.org/TR/2007/WD-powder-xsd-20070925"><cite>Protocol for Web Description Resources (POWDER): Web Description Resources Datatypes (WDRD).</cite></a> 25 September 2007. W3C Working Draft. (Work in progress.) URL: <a href="http://www.w3.org/TR/2007/WD-powder-xsd-20070925">http://www.w3.org/TR/2007/WD-powder-xsd-20070925</a>