<http://www.w3.org/1999/02/22-rdf-syntax-ns#first>
<http://ichef.bbci.co.uk/news/560/media/images/50517000/jpg/_50517330_el_sidron,_galeria_del_osario_vista_desde_el_fondo.jpg>
<http://www.bbc.com/news/science-environment-12049854>