A method of retrieving display data for a handheld display device. The method comprises the steps, in a server, of: receiving interaction data from the handheld display device, the interaction data being generated by the device using image data acquired by imaging an area of a printed substrate containing...http://www.google.com/patents/US8035850?utm_source=gb-gplus-sharePatent US8035850 - Method and system for retrieving display data
