It is not free. The database of the American Mathematical Society is not free, but a paid database. The maintenance and operation of the database requires a lot of manpower, material resources and financial resources, including data collection, sorting, updating, maintenance and technical support. Therefore, in order to ensure the normal operation and sustainable development of the database, users need to be charged. The content in the database often involves the protection of intellectual property rights, and it needs to pay a certain fee to obtain relevant authorization.