query: #works referred to by Iron Maiden songs
  SELECT ?item ?itemLabel 
        (GROUP_CONCAT(?basedOn; separator=", ") AS ?songsBasedOn) 
        (GROUP_CONCAT(?inspiredBy; separator=", ") AS ?songsInspiredBy)
        (GROUP_CONCAT(?cites; separator=", ") AS ?songsQuoting)
        (GROUP_CONCAT(?quotes; separator=", ") AS ?songsQuotingDirectly)
  WHERE {
    ?song wdt:P175 wd:Q42482; wdt:P31 wd:Q7366. 
    {?song wdt:P144 ?item. ?song rdfs:label ?label. FILTER(LANG(?label)="en") BIND (?label AS ?basedOn)} UNION
    {?song wdt:P941 ?item. ?song rdfs:label ?label. FILTER(LANG(?label)="en") BIND (?label AS ?inspiredBy)} UNION
   {?song wdt:P2860 ?item. ?song rdfs:label ?label. FILTER(LANG(?label)="en") BIND (?label AS ?cites)} UNION
    {?song wdt:P6166 ?item. ?song rdfs:label ?label. FILTER(LANG(?label)="en") BIND (?label AS ?quotes)}
    SERVICE wikibase:label { bd:serviceParam wikibase:language "[AUTO_LANGUAGE],en". }
  }
  GROUP BY ?item ?itemLabel