<P> Most libraries and booksellers display the book record for an invalid ISBN issued by the publisher . The Library of Congress catalogue contains books published with invalid ISBNs, which it usually tags with the phrase "Cancelled ISBN". However, book - ordering systems such as Amazon.com will not search for a book if an invalid ISBN is entered to its search engine . OCLC often indexes by invalid ISBNs, if the book is indexed in that way by a member library . </P> <P> Only the term "ISBN" should be used; the terms "eISBN" and "e-ISBN" have historically been sources of confusion and should be avoided . If a book exists in one or more digital (e-book) formats, each of those formats must have its own ISBN . In other words, each of the three separate EPUB, Amazon Kindle, and PDF formats of a particular book will have its own specific ISBN . They should not share the ISBN of the paper version, and there is no generic "eISBN" which encompasses all the e-book formats for a title . </P> <P> Currently the barcodes on a book's back cover (or inside a mass - market paperback book's front cover) are EAN - 13; they may have a separate barcode encoding five digits called an EAN - 5 for the currency and the recommended retail price . For 10 digit ISBNs, the number "978", the Bookland "country code", is prefixed to the ISBN in the barcode data, and the check digit is recalculated according to the EAN13 formula (modulo 10, 1x and 3x weighting on alternate digits). </P> <P> Partly because of an expected shortage in certain ISBN categories, the International Organization for Standardization (ISO) decided to migrate to a thirteen - digit ISBN (ISBN - 13). The process began 1 January 2005 and was planned to conclude 1 January 2007 . As of 2011, all the 13 - digit ISBNs began with 978 . As the 978 ISBN supply is exhausted, the 979 prefix was introduced . Part of the 979 prefix is reserved for use with the Musicland code for musical scores with an ISMN. 10 digit ISMN codes differed visually as they began with an "M" letter; the bar code represents the "M" as a zero (0), and for checksum purposes it counted as a 3 . All ISMNs are now 13 digits commencing 979 - 0; 979 - 1 to 979 - 9 will be used by ISBN . </P>

Where does the isbn number go on a book