<http://www.w3.org/1999/02/22-rdf-syntax-ns#first>
<http://ichef.bbci.co.uk/news/ws/560/amz/worldservice/live/assets/images/2014/05/28/140528194919_obama_west_point_speech_624x351_reuters.jpg>
<http://www.bbc.com/mundo/noticias/2014/05/140528_eeuu_obama_discurso_exterior_guerra_tsb.shtml>