Question: Who was in youth clubs of FC Barcelona and Newell's Old Boys?
SPARQL:
SELECT DISTINCT ?uri WHERE { ?uri <http://dbpedia.org/property/youthclubs> <http://dbpedia.org/resource/FC_Barcelona> . ?uri <http://dbpedia.org/property/youthclubs> <http://dbpedia.org/resource/Newell's_Old_Boys> . }