<http://www.w3.org/1999/02/22-rdf-syntax-ns#first>
<http://pop.h-cdn.co/assets/cm/15/05/480x360/54cb2435c549d_-_brief-history-sleds-06-1213-de.jpg>
<http://www.popularmechanics.com/adventure/sports/g1377/a-brief-history-of-the-sled/>