http://books.google.cl/books?id=nwF22tYK2eAC&pg=PA164&lpg=PA164&dq=JOR+GE+EDWARDS++Y+HAVILAND&source=bl&ots=J4bCTZGkTw&sig=NzHubAzk3Bd2LM819HYgzdF61GM&hl=es-419&sa=X&ei=2Ud4U8DnFZSksQS91IGwDg&ved=0CD0Q6AEwAg#v=snippet&q=Jorge%20EDWARDS&f=false pag 174