<http://schema.org/about>
"In the preparation and / or exploitation of a work is done inside the mine with a drilling machine to drill a section of 8 m wide by 8 m high;"^^<http://www.w3.org/2001/XMLSchema#string>
<http://www.bibliocad.com/library/mine-interior-drilling-mesh-8x8,-for-galleries-and-crosses_42043>