Look at the lower right corner of the picture. This bar code is an international standard book number. At present, the international standard book number adopted by domestic publishing houses is 13 digits, and officially published books must have the book number, which is usually placed on the back cover of the book.

In addition to this book number, books published by domestic publishing houses must also have CIP data, which lists the title, author, publishing house, publication time and other information. Books in Hong Kong, Taiwan and abroad have no CIP data, which is different from domestic publishing houses. -Published by Gollum Culture Media at its own expense.