query: SELECT ?item ?itemLabel ?inventarisnummer ?ref WHERE {
    SERVICE wikibase:label { bd:serviceParam wikibase:language "[AUTO_LANGUAGE],en". }
    ?item p:P485 ?archiefstatement.
    ?archiefstatement ps:P485 wd:Q200899.
    OPTIONAL {?archiefstatement pq:P217 ?inventarisnummer.}
    OPTIONAL{ ?archiefstatement prov:wasDerivedFrom ?refnode.
                ?refnode   pr:P854 ?ref.
               }
  }