TK Electrical engineering. Electronics Nuclear engineering HE Transportation and Communications 36 QA75 Electronic computers. Computer science 19 T Technology (General) 7 TL Motor vehicles. Aeronautics. Astronautics 7 TJ Mechanical engineering and machinery 6 QA76 Computer software 5 QA Mathematics 3 T58.5-58.64 Information technology 2 TA Engineering (General). Civil engineering (General) 2 TK5101-6720 Telecommunication 2 TK7885-7895 Computer engineer. Computer hardware 2 TR Photography 2 HD28 Management. Industrial Management 1 HD61 Risk Management 1 HG Finance 1 QP Physiology 1 R Medicine (General) 1 RZ Other systems of medicine 1 TC Hydraulic engineering. Ocean engineering 1 TH Building construction 1 TN Mining engineering. Metallurgy 1 TP Chemical technology 1 TX Home economics 1 Unspecified 1