This is a tracking category.

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.

More information:

• This category is hidden on its member pages—unless the corresponding user preference (Appearance → Show hidden categories) is set.
• These categories are used to track, build and organize lists of pages needing "attention en masse" (for example, pages using deprecated syntax), or that may need to be edited at someone's earliest convenience.
• These categories also serve to aggregate members of several lists or subcategories into a larger, more efficient list (discriminated by classifications).
• Typically, tracking categories are automatically populated by templates invoked in pages or by the MediaWiki software (see Special:TrackingCategories for an overview of the latter).

Administrators: Please do not delete this category as empty!

This category may be empty occasionally or even most of the time.

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=1929.

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