PropertyValue
http://www.w3.org/1999/02/22-rdf-syntax-ns#type
http://www.w3.org/ns/prov#value
  • Natural gas ??? Mixtures of hydrocarbon gases and vapors consisting principally of methane (CH4) in gaseous form.
http://www.w3.org/ns/prov#wasQuotedFrom
  • global-resource-energy.com