1) The version of the bibliography designated by the school is relatively old. Old teachers in some schools like to use old textbooks, so many books in the designated bibliography are very old, and some even date from the 1970s and 1980s. Such books are no longer sold in the market, so they can only be consulted and copied in the library;

2) Foreign original textbooks are generally more expensive. Generally, the price of each textbook is around 100 USD. Plus exchange rate, freight and tax rate, each textbook is at least equivalent to RMB 900 yuan. Such a high price is really prohibitive. We can copy by relying on some original textbooks at hand. The price is much lower than the original price, and the quality is good.