TJ Mechanical engineering and machinery 18 TA Engineering (General). Civil engineering (General) 4 TK Electrical engineering. Electronics Nuclear engineering 2 TS Manufactures 2 HD Industries. Land use. Labor 1 HD1394-1394.5 Real estate management 1 HD28 Management. Industrial Management 1 HD30.2 Knowledge management 1 HN Social history and conditions. Social problems. Social reform 1 HT Communities. Classes. Races 1 HX Socialism. Communism. Anarchism 1 L Education (General) 1 NA Architecture 1 T Technology (General) 1 TD Environmental technology. Sanitary engineering 1 TH Building construction 1 TH434-437 Quantity surveying 1 TP Chemical technology 1 Unspecified 1