query: #title: values for items for Emperors of Japan should be instances of Japanese era names
  # Complex constraint from [[Property talk:P6902]]
  #
  SELECT ?item ?era
  {
  	?item wdt:P39 wd:Q208233 . 
      ?item wdt:P6902 ?era . 
      MINUS { ?era wdt:P31 wd:Q24706 }
  }
  LIMIT 50