coal 205 brown coal 77 mining engineering 54 hard coal 54 mining 31 fuels (chemistry) 25 history 23 more ... combustion 20 deposits mining 17 mines (mining) 17 coal energy sources 14 deep mining 14 caustobiolite deposits 14 surface mining 14 crude oil 14 geology 13 těžba uhlí 13 opencast quarry mining 12 power engineering 11 metallurgy 11 deposit geology 11 simulation and modelling 10 mineral deposits 9 analytical chemistry 8 environment protection 8 petrography 8 solid fuels 8 biomass 7 coke industry 7 landscape recultivation 7 less ...