<http://www.w3.org/1999/02/22-rdf-syntax-ns#first>
<http://ichef-1.bbci.co.uk/news/560/media/images/68841000/jpg/_68841687_p4240081-false-colour_sem_of_rods_and_cones_of_the_retina-spl.jpg>
<http://www.bbc.com/news/health-23374623>