① Use all kinds of bibliographies and abstracts to find problems from the circulation clues of documents and find evidence to distinguish authenticity. Doubts about the authenticity of documents are the starting point of counterfeiting identification, and most of these doubts are found and put forward in circulation. As for the proof of the distinction between authenticity and falsehood, it is inseparable from the investigation of the author's life and the formation and circulation of documents from the perspective of bibliography and edition.
(2) Verify the authenticity of the book according to other cited documents. Any real document will leave traces of its form and content more or less in the process of circulation, especially the quotations from people who can see the book at that time, which can be used as strong evidence to identify the authenticity. For example, when it is found that "later generations said that a book appeared at a certain time, but people didn't see it at that time", or "A book was quoted before it was lost, but A book is not quoted by B book today" (in the words of Liang Qichao above), it can be basically concluded that this book is forged.
(3) Identify whether the literature conforms to the era of the book from the content and style. For example, we can find evidence from historical facts, academic ideas, style, grammar, language (including dialects of a specific era), appellation, formulation and so on. If the history and theory of later generations are introduced in the book, and there are language phenomena that are inconsistent with the specific era environment, at least it can be determined that there are problems in the era of the book. This method has been used to a great extent in the previous research on the authenticity of Liezi. In order to use this method more correctly, people are also required to know something about the writing of ancient books. Ancient records, especially pre-Qin documents, have their own unique style. Some famous books and records are often not written by one person at a time, but are finalized after a long period of circulation and supplement. This is different from a fake book in the strict sense. Zhang Xin said: "Generally, the fake books in the Warring States period and after the Warring States period are mostly fake books, but there are too many fake books;" The false books before and during the Warring States Period are due to readers' misunderstanding, which readers should know (General Theory of False Books).