Name all the soccer players who played in an under 18 club for La Liga?
SELECT DISTINCT ?uri WHERE { ?x <http://dbpedia.org/property/league> <http://dbpedia.org/resource/La_Liga> . ?uri <http://dbpedia.org/property/youthclubs> ?x  . ?uri <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://dbpedia.org/ontology/SoccerPlayer>}
La_Liga