query: SELECT ?artist ?item (COUNT(DISTINCT ?artwork) AS ?count)  {
    ?artwork wdt:P31 wd:Q3305213 . 
    ?artwork p:P528 ?catalogstatement .
    ?catalogstatement ps:P528 ?catalogid . 
    ?catalogstatement pq:P972 ?item .
    ?item wdt:P921 ?artist.
    ?artist wdt:P106 wd:Q1028181.
    } GROUP BY ?artist ?item
  ORDER BY ?artist