About: http://webisa.webdatacommons.org/129549732

Property	Value
http://www.w3.org/1999/02/22-rdf-syntax-ns#type	http://www.w3.org/ns/prov#Entity
http://www.w3.org/ns/prov#value	With the added attention that acid rain and other pollution problems received in the 1970s and 1980s, low-sulfur coal became increasingly more valuable.
http://www.w3.org/ns/prov#wasQuotedFrom	libertyfund.org