China Standard Book Number (ISBN) is a code consisting of 13 digits, which cannot be used under the following circumstances:
Illegal publications: Only legally published books with regular ISBN numbers can use ISBN numbers. If a book is not a legal publication and has no ISBN number, then the Chinese standard book number cannot be used.
Internal documents: Some internal documents, such as internal reports and materials of enterprises, are not regarded as official publications, so the Chinese standard book number cannot be used.
Temporary publications: some temporary publications, such as conference papers, posters, brochures, etc. Don't use ISBN number because it has a short publication time and lacks long-term preservation value.
Personal collections: Although personal collections also have ISBN numbers, they are usually not regarded as official publications, but as the author's personal collections or exhibitions.
Other circumstances that do not meet the publishing requirements: In addition to the above circumstances, if the book violates the publishing requirements, involves vulgar pornography, violent crimes, or infringes the copyright of others, the Chinese standard book number cannot be used.
In short, the Chinese Standard Book Number is a coding system for identifying official publications. Only books that meet the relevant regulations and standards can obtain ISBN number and be regarded as official publications.