identification numbers and codes[computer languages, codes, and protocols]bar codesRFIDpersistent identifiersunique identifiersmanuscript designationsidentification numbersURIsshelf markscode numbersISSNCODENDOIUPChandlesISTCISWCLCCNSICIrecord identifiersversion numbersISO 3-lettersISO 2-lettersISO 3-numbersISO 2-numbersUS Postal Service codesidentifying artifacts