Class A: Marxism-Leninism B: Philosophy C: Social Science D: Political Law E: Military F: Economy G: Culture, Science, Education, Sports H: Chinese I; Literature J- Art K- Historical Geography N- Natural Science O- Mathematical Science Chemistry P- Astronomy, Earth Science Q- Biological Science R Medical and Health S Agricultural Science T- Industrial Science TB- General Industrial Technology TD- Mining Engineering TE- Oil and Gas Engineering TF- Metallurgical Industry TG- Metallurgy, Metal Technology TH- Mechanical Instrument TJ- Weapon Industry t K- Power Engineering TL- Atomic Energy Technology TM- Electronic Technology TN- Electronic Technology

There are many small branches.