The time involved in the above papers is limited to a certain extent. When writing a paper, you need to inquire about some information related to the topic. Some materials may be too old, such as some economic theories, which may be updated with time. If you refer to papers that are too old, it may not be suitable for the current research situation. If it is some engineering research, it may not be affected by time.

When inquiring about relevant information, look at the year information at that time.