<http://www.w3.org/1999/02/22-rdf-syntax-ns#first>
<http://ichef-1.bbci.co.uk/news/ws/560/amz/worldservice/live/assets/images/2012/11/13/121113131539_materia1_304x171_ap_nocredit.jpg>
<http://www.bbcmundo.com/mundo/noticias/2012/11/121113_mapa_energia_oscura_am.shtml>