PREFIX : <http://example/>
PREFIX  afn:     <http://jena.hpl.hp.com/ARQ/function#>
PREFIX  rdf:    <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX  rdfs:   <http://www.w3.org/2000/01/rdf-schema#>
PREFIX  apf:     <http://jena.hpl.hp.com/ARQ/property#>

SELECT ?x
{
    ?x :p ?v 
}
GROUP BY ?x
HAVING (count(?v)>1)