query: #defaultView:BarChart
  SELECT ?retrieved ?count WITH {
    SELECT ?retrieved (COUNT(?reference) AS ?count) WHERE {
      ?reference pr:P813 ?retrieved.
    }
    GROUP BY ?retrieved
  } AS %results WHERE {
    INCLUDE %results.
    wd:Q2013 wdt:P571 ?wikidataInception.
    FILTER(?retrieved >= ?wikidataInception && ?retrieved <= NOW())
  }