In item B, the Chinese standard book number and its barcode and pricing should be printed in the lower right corner of the back cover of the book. When the width of the spine is less than 5 mm and it is impossible to print words, the edge name can be printed on the upper part of the back cover with the edge of the spine not exceeding15 mm. Item C, also known as "envelope", is a piece of paper with no fixed package outside the hard (or thick) cover, which can protect the cover, so it is called "envelope". Must be made of paper with high fastness, front and back cuffs.