<http://www.w3.org/1999/02/22-rdf-syntax-ns#first>
<http://pop.h-cdn.co/assets/cm/15/05/480x480/54caa39bb9ea9_-_lanthanum-0510-xln.jpg>
<http://www.popularmechanics.com/science/environment/g282/important-rare-earth-elements/>