Question: List the subjects of the books whose one of the topics is Pau Broca ?
SPARQL:
SELECT DISTINCT ?uri WHERE { ?x <http://dbpedia.org/property/subject> <http://dbpedia.org/resource/Paul_Broca> . ?x <http://dbpedia.org/property/subject> ?uri  . ?x <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://dbpedia.org/ontology/Book>}