query: prefix prov: <http://www.w3.org/ns/prov#>
  PREFIX wikibase: <http://wikiba.se/ontology#>
  prefix pr: <http://www.wikidata.org/prop/reference/>
  PREFIX wd: <http://www.wikidata.org/entity/>
  PREFIX ps: <http://www.wikidata.org/prop/statement/>
  SELECT ?source ?sourceLabel (count(?source) as ?mentions)
  WHERE {
       ?statement ps:P4976 ?one .
    ?statement prov:wasDerivedFrom ?ref .
    ?ref pr:P143 ?source .
       SERVICE wikibase:label {
      bd:serviceParam wikibase:language "lv,en" .
     }
  }
  group by ?source ?sourceLabel
  ORDER BY DESC(?mentions)