Category:Articles with invalid ISSNs

This is a maintenance category. It is used for maintenance of the Wikipedia project and is not part of the encyclopedia. It contains pages that are not articles, or it groups articles by status rather than content. Do not include this category in content categories. This is a hidden category. It is not shown on its member pages, unless the corresponding user preference 'Show hidden categories' is set. This is a tracking category. It builds and maintains a list of pages primarily for the sake of the list itself. Pages are added to tracking categories through templates.

Administrators: Please do not delete this category even if it is empty! This category may be empty occasionally or even most of the time.

This is a maintenance category of articles with invalid ISSNs. It is often included by means to the template {{Please check ISSN}}, which should be located next to the ISSN with the problem.

The most likely reason is a bad checksum, (see ISSN) which probably means there is a typing error in the ISSN.