An optically readable record for storing encoded information comprises (1) a recording medium, (2) a self-clocking data code for encoding the information, with this data code being composed of glyphs that are written in a two dimensional code field on the recording medium on centers that are spatially...http://www.google.ca/patents/US5521372?utm_source=gb-gplus-sharePatent US5521372 - Framing codes for robust synchronization and addressing of self-clocking glyph codes
