Which training institutions are more powerful in Sichuan teacher recruitment examination training?

There are many teacher recruitment examination and training institutions in Sichuan, among which Zhonggong, Bocheng, Tuhua and Shanxiang are more powerful. Because they are not only established for a long time, but also famous in the industry, and only these four companies in Sichuan are qualified to publish such books. No other organization has the right to publish books.