About: http://webisa.webdatacommons.org/339565156

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	As is known in the art, one of these surfaces may preferably be spherical to correct defocus aberrations, with or without a cylindrical component to correct astigmatism.
http://www.w3.org/ns/prov#wasQuotedFrom	google.es