Hello, the content of the textbook will be checked again. The content of the book may be repetitive, that is to say, the content of the book can be found through paper duplicate checking, but it has certain limitations, that is, only when the content of the book is included in the paper duplicate checking system, the content of the book we quoted will be repetitive. Therefore, when we quote the contents of books, it is best to add reference symbols or make appropriate modifications to ensure safety and avoid duplication. Paper book resources are included in the database of paper duplicate checking system, and some paper book resources can be copied, but not all paper book resources will be included in the database of paper duplicate checking system. Some old paper books are not included in the paper duplicate checking system. Of course, it also depends on the specific paper duplicate checking system. The paper book duplicate checking system contains many paper book resources. Some authoritative paper duplicate checking systems have a lot of contents in the database resources, and naturally they also contain a lot of paper book resources. However, not all books are identified and included in the paper duplicate checking database, and different paper duplicate checking systems contain different book content resources. Therefore, if the contents of the cited books in our paper are included in the database of the paper duplicate checking system, then these quotations can be repeated and the repetition rate can be calculated.