<http://www.w3.org/1999/02/22-rdf-syntax-ns#first>
<http://ichef.bbci.co.uk/news/ws/560/amz/worldservice/live/assets/images/2013/11/22/131122114059_nasa_burst_624x351_nasaswiftcruzdewilde.jpg>
<http://www.bbc.com/mundo/noticias/2013/11/131122_ciencia_explosion_rayos_gamma_supernova_np.shtml>