About: http://webisa.webdatacommons.org/16145990

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	The main technological challenge was a lack of strong-enough materials, but now we have materials such as carbon nanotubes and graphene that are much stronger than steel.
http://www.w3.org/ns/prov#wasQuotedFrom	issuu.com