PREFIX foaf: <http://xmlns.com/foaf/0.1/>
PREFIX dc: <http://purl.org/dc/elements/1.1/>

SELECT DISTINCT ?name ?source ?date

FROM  <urn:x-local:details>
GRAPH <urn:x-local:graph1> 
GRAPH <urn:x-local:graph2>

WHERE SOURCE ?snode (?person foaf:name ?name)
      (?snode dc:source ?source)
      (?snode dc:date   ?date)