1. Various ways to interpret files. Because historical documents have complex historical background and cultural connotation, the same document may be interpreted and understood by different people in different ways.

2. Various uses of literature. Historical documents can be used to understand historical events, cultural background, social features and other aspects of information, but also can be used to prove a certain point of view or discuss the truth of a historical event.

3. Various literature sources. Historical documents come from a wide range of sources, including historical archives, personal diaries, biographies, literary works and other forms, each of which will bring different historical information and cultural connotations.