Such books are hard to find if they are to be applied. Books sold on the beach are full of mistakes; Bookstores sell them out of context. Even in the second-hand book market, there are few really practical reference books. Because such books are rarely reprinted after the founding of the People's Republic of China, most of them are mainly copied. Even if a few books are published, there are not many in society. Some of its contents are also very different from those in the western region and abroad.