<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/2014/05/01/140501152040_beta_pictoris_464x261_esodigitizedskysurvey2.jpg>
<http://www.bbc.com/mundo/noticias/2014/05/140501_ciencia_planeta_beta_pictoris_b_dia_ocho_horas_np.shtml>