QA76 Computer software QA75 Electronic computers. Computer science 45 HD28 Management. Industrial Management 16 TA Engineering (General). Civil engineering (General) 9 HE Transportation and Communications 7 TK Electrical engineering. Electronics Nuclear engineering 7 HF Commerce 6 Q Science (General) 6 T Technology (General) 6 QA Mathematics 5 HD Industries. Land use. Labor 4 TD Environmental technology. Sanitary engineering 3 TJ Mechanical engineering and machinery 3 TP Chemical technology 3 H Social Sciences (General) 2 HG Finance 2 L Education (General) 2 LB Theory and practice of education 2 LB1603 Secondary Education. High schools 2 TS Manufactures 2 GA Mathematical geography. Cartography 1 LB2300 Higher Education 1 NA Architecture 1 QC Physics 1 QD Chemistry 1 RZ Other systems of medicine 1 S Agriculture (General) 1 SB Plant culture 1 TC Hydraulic engineering. Ocean engineering 1 TE Highway engineering. Roads and pavements 1