query: SELECT ?item WHERE {
    ?item wdt:P31 wd:Q5 .
    ?item p:P91 [
      prov:wasDerivedFrom ?ref
    ] .
    ?ref pr:P143 [] .
    FILTER NOT EXISTS {
      ?item p:P91 [
       prov:wasDerivedFrom ?ref2 
      ] 
      FILTER (?ref2 != ?ref ) 
      FILTER NOT EXISTS { ?ref2 pr:P143 [] } .
    }
  }