More topics under "E21 - Earth or rock drilling; Mining" (397,450) |
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E21B - Earth or rock drilling; Obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells (326,851) |
E21C - Mining or quarrying (17,971) |
E21D - Shafts; Tunnels; Galleries; Large underground chambers (32,005) |
E21F - Safety devices, transport, filling-up, rescue, ventilation, or drainage in or of mines or tunnels (20,623) |