PropertyValue
http://www.w3.org/1999/02/22-rdf-syntax-ns#type
http://www.w3.org/ns/prov#value
  • UPDATE: Random Walk has apparently solved your problem, but here is a slightly different version of the same solution anyway... (possibly a bit less different from the OP code, possibly a little simpler, and, well, at least this allows my reply to have some usable content):
http://www.w3.org/ns/prov#wasQuotedFrom
  • perlmonks.org