query: #Name, foundation year, and flag of the capital cities of the EU countries.
  #Duplicate entry for Amsterdam (two countries), Vienna (two flags), Vilnius (two years).
  
  SELECT ?item ?itemLabel ?capitalLabel ?founded ?flag
  WHERE {
    ?item wdt:P463 wd:Q458;
          wdt:P36 ?capital.
  OPTIONAL  {?capital wdt:P41 ?flag.}
  OPTIONAL  {?capital wdt:P571 ?founded.}
    
  SERVICE wikibase:label {bd:serviceParam wikibase:language "[AUTO_LANGUAGE],en" }
  }
  ORDER BY (?capitalLabel)
  