International Standard Book Numbers (ISBNs)—those ten- or thirteen-digit numbers that identify books—are changing yet again. Currently, they’re transitioning from the 10-digit variety (which is only used within the publishing and bookstore realm) to the 13-digit version (which can be read by all bar-code scanners). Most books currently carry both versions (the 10-digit number becomes 13 by adding 978 at the front and changing the check-digit at the end), but starting in early 2008, a new prefix will be added, 979. This addition means the 10-digit ISBNs will no longer be unique, and thus will have to be phased out.