<http://webisa.webdatacommons.org/441332379>	<http://www.w3.org/ns/prov#wasQuotedFrom>	<google.ca> .
<http://webisa.webdatacommons.org/prov/10808548>	<http://www.w3.org/ns/prov#wasDerivedFrom>	<http://webisa.webdatacommons.org/441332379> .
<http://webisa.webdatacommons.org/441332379>	<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>	<http://www.w3.org/ns/prov#Entity> .
<http://webisa.webdatacommons.org/441332379>	<http://www.w3.org/ns/prov#value>	"Further, it is especially difficult to fabricate such lenses with a focal length sufficient to maintain a reasonable working distance from the workpiece." .