1. From the protection period, it can be inferred whether the patent naturally terminates as invalid due to the expiration of the protection period.
2. Determine the legal status by consulting the patent register of the national patent office. Go directly to the official websites of patent offices in various countries or the website of the European Patent Office to download the original text for free. You can also inquire through the related link of "Major Foreign Intellectual Property Websites" on China National Intellectual Property Administration website.