query: PREFIX wd: <http://www.wikidata.org/entity/> 
  PREFIX wdt: <http://www.wikidata.org/prop/direct/>
  PREFIX schema: <http://schema.org/>
  
  SELECT ?author (COUNT(distinct ?sitelink) as ?count) WHERE {
    ?work wdt:P50 ?author . 
    ?sitelink schema:about ?author .
    FILTER NOT EXISTS { ?author wdt:P214 ?viaf }
   } GROUP BY ?author ORDER BY DESC(?count)