<http://www.w3.org/1999/02/22-rdf-syntax-ns#first>
<http://ichef.bbci.co.uk/news/560/media/images/51368000/jpg/_51368661_f001662-metastasis_of_a_cancerous_cell,_sem-spl.jpg>
<http://www.bbc.co.uk/news/health-12525109>