<http://www.w3.org/1999/02/22-rdf-syntax-ns#first>
<http://ichef.bbci.co.uk/news/ws/560/amz/worldservice/live/assets/images/2014/04/11/140411103937_energia_fracking_304x171_getty.jpg>
<http://www.bbc.com/mundo/noticias/2014/04/140410_eeuu_energia_independencia_finde_wbm.shtml>