query: #title: Two category items linking to the same Commons category
  # Complex constraint from [[Property talk:P373]]
  # Generally only one category item should link to a Commons category
  SELECT DISTINCT ?item ?item2 ?value {
    ?item wdt:P373 ?value .
    ?item wdt:P31 wd:Q4167836 .
    ?item2 wdt:P373 ?value .
    ?item2 wdt:P31 wd:Q4167836 .
    FILTER( ?item != ?item2 && STR( ?item ) < STR( ?item2 ) ) .
  }
  LIMIT 1000