<http://www.w3.org/1999/02/22-rdf-syntax-ns#first>
<http://ichef.bbci.co.uk/news/ws/560/amz/worldservice/live/assets/images/2013/11/19/131119181721_facebook_logo_304x171_afp_nocredit.jpg>
<http://www.bbc.com/mundo/blogs/2013/12/131204_blog_un_mundo_feliz_david_cuen_google_plus.shtml?postId=118081469>