<http://www.w3.org/1999/02/22-rdf-syntax-ns#first>
<http://ichef.bbci.co.uk/news/ws/560/amz/worldservice/live/assets/images/2012/11/27/121127155807_wave_976x549_marktipple.jpg>
<http://www.bbc.com/mundo/video_fotos/2012/12/121201_galeria_fotos1_subacuaticas_oceanos_tsb.shtml>