query: #defaultView:Graph
  SELECT DISTINCT
    (SAMPLE(?item) as ?river)
    (SAMPLE(COALESCE(?en_label, ?item_label)) as ?riverLabel)
    (SAMPLE(?mouth) as ?mouth)
  WHERE {
    ?item wdt:P17 wd:Q28. # Limit to rivers of Hungary, because otherwise 400k+ results.
    ?type wdt:P279* wd:Q355304. # Watercourse
    ?item p:P31/ps:P31 ?type.
    ?item wdt:P403 ?mouth.
    OPTIONAL {?item rdfs:label ?en_label. FILTER(LANG(?en_label) = "en")} OPTIONAL {?item rdfs:label ?item_label}
  } GROUP BY ?item