deep mining history 19 mining engineering 18 mines (mining) 15 hard coal 8 mining 6 mine exploitation 5 more ... landscape recultivation 5 safety of work 4 coal-getting machines 4 uranium 4 deposits mining 3 workings 3 rock bumps 3 geomechanics 3 illumination 3 crude oil 3 ore deposits 3 coal 3 environment 3 safety 2 mining machine industry 2 openings 2 vertical working 2 mining transport machines 2 blasts 2 mine rescue 2 geology 2 brown coal 2 thrift 2 less ...