TJ Mechanical engineering and machinery 107 TS Manufactures 57 TK Electrical engineering. Electronics Nuclear engineering 29 TA Engineering (General). Civil engineering (General) 27 T Technology (General) 24 HD28 Management. Industrial Management 19 TP Chemical technology 14 HD Industries. Land use. Labor 12 QA75 Electronic computers. Computer science 12 Q Science (General) 7 QA76 Computer software 7 QD Chemistry 7 QA Mathematics 6 TD Environmental technology. Sanitary engineering 5 TH Building construction 5 H Social Sciences (General) 4 QC Physics 3 QH Natural history 3 Unspecified 3 G Geography (General) 2 G70.212-70.215 Geographic information system 2 HF Commerce 2 QE Geology 2 T Technology 2 GE Environmental Sciences 1 HD61 Risk Management 1 HE Transportation and Communications 1 HF5549.5.M63 Employee motivation 1 Q Science 1 QK Botany 1