query: SELECT ?item ?itemLabel ?itemDescription ?earliestdate ?latestdate ?averageyear ?creator ?creatorLabel ?creatorDescription ?dob ?dod WHERE {
    ?item wdt:P31 wd:Q3305213;
      p:P571 ?inceptionstatement .
    ?inceptionstatement ps:P571 ?inception.
    FILTER(wikibase:isSomeValue(?inception)) .
    MINUS { ?inceptionstatement pq:P1319 ?tooearly . FILTER(YEAR(?tooearly) < 500) }
    MINUS { ?inceptionstatement pq:P1326 ?latetooearly . FILTER(YEAR(?latetooearly) < 500) }
    OPTIONAL { ?inceptionstatement pq:P1319 ?earliestdate ;
                                   pq:P1326 ?latestdate .
             BIND(((YEAR(?earliestdate)+YEAR(?latestdate))/2) AS ?averageyear )
    }
    OPTIONAL { ?item wdt:P170 ?creator .
              OPTIONAL { ?creator wdt:P569 ?dob }
              OPTIONAL { ?creator wdt:P570 ?dod }
              }
    SERVICE wikibase:label { bd:serviceParam wikibase:language "[AUTO_LANGUAGE],en". }
  }