query: PREFIX wd: <http://www.wikidata.org/entity/>
  PREFIX wdt: <http://www.wikidata.org/prop/direct/>
  PREFIX wikibase: <http://wikiba.se/ontology#>
  PREFIX p: <http://www.wikidata.org/prop/>
  PREFIX v: <http://www.wikidata.org/prop/statement/>
  PREFIX q: <http://www.wikidata.org/prop/qualifier/>
  PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
  #biographical articles published in DNB00,DNB01,DNB12
  #with author missing
  SELECT ?instance ?instance_label ?publication_label (count(distinct ?DNBentry ) as ?number) 
  WHERE 
  {    	{ ?DNBentry wdt:P1433 wd:Q15987216 . } #DNB00
    UNION { ?DNBentry wdt:P1433 wd:Q16014700 . } #DNB01
    UNION { ?DNBentry wdt:P1433 wd:Q16014697 . } #DNB12
    UNION { ?DNBentry wdt:P1433 wd:Q1210343 . } #DNB
  	?DNBentry wdt:P31 	wd:Q19389637 . #articles only, not cross-references
   	?DNBentry wdt:P31 	?instance .
     ?DNBentry wdt:P1433  ?publication
    OPTIONAL 	{?DNBentry wdt:P50  	?author} .
   OPTIONAL 	{?publication rdfs:label ?publication_label filter (lang(?publication_label) = "en") .} 
   OPTIONAL 	{?instance rdfs:label ?instance_label filter (lang(?instance_label) = "en") .} 
     FILTER 	(!bound(?author))
  } GROUP BY ?instance ?instance_label ?publication_label
  ORDER BY ?publication_label