TK Electrical engineering. Electronics Nuclear engineering 49 TJ Mechanical engineering and machinery 19 QA75 Electronic computers. Computer science 8 QA76 Computer software 4 QA Mathematics 3 TL Motor vehicles. Aeronautics. Astronautics 2 GB Physical geography 1 L Education (General) 1 LB Theory and practice of education 1 PN Literature (General) 1 QE Geology 1 QH301 Biology 1 RZ Other systems of medicine 1 TA Engineering (General). Civil engineering (General) 1 TG Bridge engineering 1 TK5101-6720 Telecommunication 1 TS Manufactures 1 VM Naval architecture. Shipbuilding. Marine engineering 1