<http://www.w3.org/1999/02/22-rdf-syntax-ns#first>
<http://ichef.bbci.co.uk/news/ws/560/amz/worldservice/live/assets/images/2010/03/16/100316124838_hipertension_226.jpg>
<http://www.bbc.com/mundo/noticias/2013/03/130307_salud_sal_contra_sistema_inmune_ng.shtml>