query: SELECT ?i1 ?i1Label ?i2 ?i2Label ?val where {
    ?i1 wdt:P1566 ?val .
    ?i2 wdt:P1566 ?val .
    filter( !(?i1 = ?i2) && str(?i1) < str(?i2) )
    SERVICE wikibase:label {
  		bd:serviceParam wikibase:language "en,fr,sv" .
    }
  }
  limit 50