<http://webisa.webdatacommons.org/214011686>	<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>	<http://www.w3.org/ns/prov#Entity> .
<http://webisa.webdatacommons.org/214011686>	<http://www.w3.org/ns/prov#wasQuotedFrom>	<google.com> .
<http://webisa.webdatacommons.org/prov/145763856>	<http://www.w3.org/ns/prov#wasDerivedFrom>	<http://webisa.webdatacommons.org/214011686> .
<http://webisa.webdatacommons.org/214011686>	<http://www.w3.org/ns/prov#value>	"Heretofore, considerable difficulty has been encountered in connection with the commercial cleaning of air ducts as, for example, hot air furnace ducts, air conditioning ducts, ventilating ducts and the like such as are commonly employed in large office buildings, factories, foundries, laundries, and other commercial establishments too numerous to mention." .