query: SELECT ?document ?documentLabel (COUNT(?signatory) AS ?count) WHERE {
    ?document wdt:P1891 ?signatory.
    SERVICE wikibase:label { bd:serviceParam wikibase:language "en", "fr", "he", "pt", "id". }
  }
  GROUP BY ?document ?documentLabel
  HAVING(?count > 1)
  ORDER BY DESC(?count)