query: SELECT DISTINCT ?item ?itemLabel ?output WHERE {
    ?item rdfs:label ?label.
    ?item wdt:P650 ?rkd.
    SERVICE wikibase:label { bd:serviceParam wikibase:language "nl, en". }
    FILTER((LANG(?label)) = "nl")
    BIND(REPLACE(STR(?label),"[ ]{2,}"," ") AS ?output) .
    FILTER(REGEX(?label, "[ ]{2,}"))
  }