<http://webisa.webdatacommons.org/prov/17382233> <http://www.w3.org/ns/prov#wasDerivedFrom> <http://webisa.webdatacommons.org/82245493> . <http://webisa.webdatacommons.org/82245493> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://www.w3.org/ns/prov#Entity> . <http://webisa.webdatacommons.org/prov/122776852> <http://www.w3.org/ns/prov#wasDerivedFrom> <http://webisa.webdatacommons.org/82245493> . <http://webisa.webdatacommons.org/82245493> <http://www.w3.org/ns/prov#value> "Most often, stains are metals such as iron, copper or manganese." . <http://webisa.webdatacommons.org/82245493> <http://www.w3.org/ns/prov#wasQuotedFrom> <backyardcitypools.com> .