TJ Mechanical engineering and machinery T Technology (General) TP155 Chemical engineering TD Environmental technology. Sanitary engineering TJ170 Mechanics applied to machinery. Dynamics TK2896 Production of electricity by direct energy conversion HD9502 Energy industries. Energy policy. Fuel trade TD878 Special types of environment Including soil pollution TJ181 Mechanical movements TJ807 Renewable energy sources TJ836 Hydraulic machinery TK1001 Production of electric energy or power. Powerplants. Central stations TP Chemical technology TP315 Fuel air pollution noise pollution ETD HF1040 Commodities. Commercial products HF5410 Marketing. Distribution of products LB Theory and practice of education LB2331.7 Teaching personnel LB2361 Curriculum LC Special aspects of education QC120 Descriptive and Experimental mechanics QD450 Physical and theoretical chemistry TA349 Mechanics of engineering. Applied mechanics TD194 Environmental effects of industries and plants TD783 Municipal refuse. Solid wastes TJ1125 Machine shops and machine shop practice TJ212 Control engineering systems. Automatic machinery (General) TJ241 Machine construction (General) TK3001 Distribution or transmission of electric power TK301 Electric meters TK452 Electric apparatus and materials. Electric circuits. Electric networks TK9900 Electricity for amateurs. Amateur constructors' manuals TL Motor vehicles. Aeronautics. Astronautics TP670 Oils TS155 Production management. Operations management TS200 Metal manufactures. Metalworking Tehnik hidraulis and waxes fats