The periodical number of the paper is divided into ISSN (International Standard Serial Publication Number) and CN (Domestic Unified Serial Publication Number). ISSN is an international standard code for serial publications based on the international standard ISO3297, which aims to make each serial publication with different titles and versions have an internationally unique code identification. CN serial number, also known as the serial number of domestic publications. It is a periodical identification number approved by the State Press and Publication Administration.