Category:Articles with invalid ISSNs

This is a maintenance category, used for maintenance of the Wikipedia project. It is not part of the encyclopedia and contains non-article pages, or groups articles by status rather than subject. Do not include this category in content categories. This is a tracking category. It builds and maintains a list of pages primarily for the sake of the list itself. They are not part of the encyclopedia's categorization scheme. This category is hidden on its member pages—unless the corresponding user preference (appearance → show hidden categories) is set. These categories can be 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).

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 for articles with invalid ISSNs. It is sometimes added by the template {{Please check ISSN}}, which should be located next to the ISSN with the problem. Articles can also be included in this category if an ISSN used in an {{ISSN}} or {{ISSN link}} template is not valid. The most likely reason is a bad checksum, (see ISSN) which probably means there is a typing error in the ISSN. Also, ISSNs that are not eight digits in a 4-4 pattern (i.e.: ISSN 1234-5678) will return an error message. Use an upper-case "X", not a lower-case "x", if "X" is the final character in the ISSN. The two groups of four characters are joined with a hyphen, not a dash. See also Category:CS1 errors: ISSN