About: http://webisa.webdatacommons.org/155770382

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 trick (as evidenced by your and other answers) was to do the group by first.
http://www.w3.org/ns/prov#wasQuotedFrom	stackoverflow.com