About: http://webisa.webdatacommons.org/364406554

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	Yahoo or Gmail might have enough information to do it though, especially if the user visted using the same browser both times.
http://www.w3.org/ns/prov#wasQuotedFrom	superuser.com