PropertyValue
http://www.w3.org/1999/02/22-rdf-syntax-ns#type
http://www.w3.org/ns/prov#value
  • Naturally, the quality and safety of water in these wells is an issue of concern, and in 2009, the U.S. Geological Survey (USGS) studied the water quality of over 2,000 private wells to measure the existence and extent of contamination.
http://www.w3.org/ns/prov#wasQuotedFrom
  • usgs.gov