query: #title: Spouse dies before person is born
  # Complex constraint from [[Property talk:P26]]
  #
  SELECT ?item ?spouse WHERE { 
    ?item wdt:P26 ?spouse . 
    ?item p:P569/psv:P569/wikibase:timeValue ?birth . 
    ?spouse p:P570/psv:P570/wikibase:timeValue ?death_of_spouse . 
    FILTER (?birth > ?death_of_spouse)
  }