A method of obtaining an MP3 file, the method including providing a plurality of separately identifiable MP3 files; associating each of the plurality with one or more identities; providing at least one substrate visually identifying at least one MP3 file, the file also being identified by an encoded...http://www.google.de/patents/US7218978?utm_source=gb-gplus-sharePatent US7218978 - System for retrieving and playing MP3 files
