This category is populated by {{ISBNT}} and {{ISBN}} (with parameter invalid#=yes) and by {{Listed Invalid ISBN}}, to indicate that although the given ISBN is malformed it is indeed printed on the work. These malformed ISBNs can still be looked up via Special:BookSources in the usual way despite the prominent warning — it just means that fewer Find this book links will actually work (most libraries will work, most dotcoms won't).

This is a tracking category. It is used to build and maintain 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 sub-categories 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.

Some ISBNs may still have been printed correctly elsewhere in the same book or corrected in later editions; if further research shows that to be the case (and that the new ISBN still refers to an edition with the same information on the same pages), then the invalid# parameter should be moved or {{Listed Invalid ISBN}} should be replaced with {{ISBN}}.

This is not an error category and pages in this category should be "fixed" only if the parameter has been misused (see Help:CS1 errors#bad isbn).

Articles are listed in this category when the invalid# parameter is used regardless of the validity of the ISBN.

• Category:Articles with invalid ISBNs
• Category:CS1 errors: ISBN
• Category:Pages with ISBN errors