query: SELECT ?item ?stardate ?pub
  WHERE
  {
    ?item wdt:P179 wd:Q1077 . 
    ?item wdt:P31 wd:Q61220733 .
    OPTIONAL { ?item p:P840 [ pq:P4895 ?stardate ] }
    ?item wdt:P577 ?pub .
    FILTER NOT EXISTS { ?item wdt:P577 ?pub2 . FILTER( ?pub2 < ?pub ) }
  }
  ORDER BY ?pub