<http://schema.org/keywords>
"topography, tunnels, mining, mining, drilling, Bergbau, Bohr, l'exploitation mini\u00E8re, le forage, minera\u00E7\u00E3o, perfura\u00E7\u00E3o"^^<http://www.w3.org/2001/XMLSchema#string>
<http://www.bibliocad.com/library/mine-workings_62023>