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.com/patents/US6182901?utm_source=gb-gplus-sharePatent US6182901 - Orientational disambiguation for self-clocking glyph codes
