<http://www.w3.org/1999/02/22-rdf-syntax-ns#first>
<http://pop.h-cdn.co/assets/cm/15/05/54cb1a07de3f1_-_how-it-works-sailboat-01-0913-mdn.jpg>
<http://www.popularmechanics.com/technology/a9400/how-to-make-a-sailboat-fly-15890011/>