query: #title: Check location (with the prefix EXT)
  # Complex constraint from [[Property talk:P2584]]
  #
  SELECT ?item ?value ?loc {
  	?item wdt:P2584 ?value;
            wdt:P131 ?loc.
    FILTER (SUBSTR(?value, 1, 3) = "EXT")
    FILTER NOT EXISTS {
      ?loc p:P31 [ ps:P31 wd:Q11687019 ].
    }
    FILTER NOT EXISTS {
      ?item wdt:P31 wd:Q11687019.
    }
  }