query: 
  SELECT (COUNT(?person) as ?count)  WHERE {
      #?person wdt:P31 wd:Q5. 
      ?person wdt:P21 wd:Q6581097.
      ?person wdt:P569 ?born.
      FILTER (?born >= "1950-01-01T00:00:00Z"^^xsd:dateTime) .
      ?article schema:about ?person .
      
    # look for articles (sitelinks) in de )
    	OPTIONAL { ?sitelink schema:about ?item . ?sitelink schema:inLanguage "de" }
  	#  select items with such article
  	FILTER (BOUND(?sitelink))
    #?article schema:isPartOf <https://de.wikipedia.org/>.
      
      SERVICE wikibase:label {
         bd:serviceParam wikibase:language "de"
      }
  }
  LIMIT 50