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It is used to build and maintain a list or lists of pages—primarily for the sake of the lists themselves and their use in article and category maintenance. It is not part of the encyclopedia's categorization scheme.

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This is a tracking category for book and encyclopedia citations implemented with {{citation}} templates and for book and encyclopedia citations implemented with {{cite book}} and {{cite encyclopedia}} that have |isbn= and when the publication date is before 1965.

Help desk

ISBN / Date incompatibility – this error message hidden by default

ISBNs were created c. 1965. Books published before that date will not have been issued an ISBN. However, reissues of pre-ISBN publications are issued ISBNs, even barring the publication of a new edition. Consider double-checking whether the ISBN is valid before removing it.

To resolve this error:

• Remove the ISBN when citing a source published before 1965.
  • If the cited edition or reissue of the book was published after 1965, ensure that |date= or |year= has the correct publication year. The reissue date is typically available by querying WorldCat with the reissue's ISBN. Adding |orig-date= may be appropriate in such cases; e.g., |orig-date=1st Pub. 1929.

Pages with this error are automatically placed in Category:CS1 errors: ISBN date.^[a]