query: SELECT ?inventor ?inventorLabel ?gadet ?gadgetLabel
  WHERE {
    ?inventor wdt:P157 ?gadget .
    ?gadet wdt:P61 ?inventor .
    SERVICE wikibase:label { 
      bd:serviceParam wikibase:language "en" . 
      ?inventor rdfs:label ?inventorLabel .
      ?gadget rdfs:label ?gadgetLabel .
    }
  }