"Web Content Accessibility Guidelines 2.0," B. Caldwell, M. Cooper, L. Guarino Reid, and G. Vanderheiden, eds., W3C Working Draft 11 December 2007. This W3C Working Draft is available at http://www.w3.org/TR/2007/WD-WCAG20-20070517/. The latest version of WCAG 2.0 is available at http://www.w3.org/TR/WCAG20/