<http://www.w3.org/1999/02/22-rdf-syntax-ns#first>
<http://pop.h-cdn.co/assets/cm/15/05/54cad0c04af61_-_crowd-counting-0911-de.jpg>
<http://www.popularmechanics.com/science/a7121/the-curious-science-of-counting-a-crowd/>