It can be classified according to the classification of libraries: A Marxism-Leninism, Mao Zedong Thought, Deng Xiaoping Theory B Philosophy C Introduction to Social Sciences D Politics, Law E Military F Economy G Culture, Science, Education, Sports H Language, Literature I Art K History, Geography N Introduction to Natural Sciences O Mathematical Chemistry P Astronomy, Earth Science Q Biological Sciences R Medicine, Health S Agricultural Science T Industrial Technology U Transportation V Aviation, Aerospace X Environmental Science, and Labor Protection Science (Safety Science) Z Comprehensive. Second, the category code of the book; Third, the location of the book; Fourth, there are several such books.