2. Commonly used retrieval tools include: various patent reference books, such as patent classification table, patent abstract, patent catalogue bulletin, patentee index, patent bulletin, etc. Searching for patents can be classified by patents or inventors. The steps of searching by patent classification are: searching patent names and translating names in different languages; Find the patent classification number in alphabetical order; Use the classification table to check or further find the classification number of the subject; Search the patent number according to the classification number; Search the abstract of patent specification by patent number. The steps of searching by the inventor's name are as follows: verify the name of the patentee or its company and the name of the patent itself through the patentee index; Search the abstract of patent specification by patent number.