About: http://webisa.webdatacommons.org/374759049

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	Kinda, there is a work around to do what you want, while doing the search, you can specify that results should not have some text, by using the field does not have, and include in this field some text from the signatures.
http://www.w3.org/ns/prov#wasQuotedFrom	stackexchange.com