query: PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>
  
  SELECT ?qid ?nr ?DT
  WHERE {
      ?qid wdt:P179 wd:Q57814450.
      ?qid wdt:P31 wd:Q21191270.
      ?qid p:P179 ?series.
      ?series pq:P1545 ?nr.
      OPTIONAL {
        ?qid rdfs:label ?DT.
        FILTER (LANG(?DT) = "de").
      }
  }
  GROUP BY ?qid ?nr ?DT
  ORDER BY xsd:integer(?nr)