query: #title: Check units
  # Complex constraint from [[Property talk:P2129]]
  # Unit must to be a [[d:Q60026969|unit of concentration <small>(Q60026969)</small>]]
  SELECT ?item ?unit
  WHERE {
    ?item p:P2129/psv:P2129/wikibase:quantityUnit ?unit.
    MINUS {
      ?unit wdt:P31/wdt:P279* wd:Q60026969.
    }.
  }