<http://www.w3.org/1999/02/22-rdf-syntax-ns#first>
<http://ichef.bbci.co.uk/news/ws/560/amz/worldservice/live/assets/images/2016/02/11/160211191323_stephen_hawking_624x351_reuters_nocredit.jpg>
<http://www.bbc.com/mundo/noticias/2016/02/160211_hawking_ondas_gravitacionales_agujeros_negros_ab>