A method of enabling recorded audio to be associated with a location on a surface is provided. The surface has coded data printed thereon, which is indicative of a plurality of locations on the surface. The method comprises the steps of: interacting with the surface using an optical sensing device comprising...http://www.google.de/patents/US7650197?utm_source=gb-gplus-sharePatent US7650197 - Method of associating audio with a position on a surface
