Most travel passports worldwide are MRPs. They are standardized by the "ICAO Document 9303" (endorsed by the International Organization for Standardization and the International Electrotechnical Commission as ISO/IEC 7501-1) and have a special "machine-readable zone" ("MRZ"), which is usually at the bottom of the identity page at the beginning of a passport. The "ICAO Document 9303" describes three types of documents. Usually passport booklets are issued in "Type 3" format, while identity cards and passport cards typically use the "Type 1" format.