<http://www.w3.org/1999/02/22-rdf-syntax-ns#first>
<http://pop.h-cdn.co/assets/cm/15/05/54cb1bf990d5b_-_colosseum-0913-hqq0jr-mdn.jpg>
<http://www.popularmechanics.com/culture/a9539/can-math-predict-the-rise-and-fall-of-empires-15960155/>