<http://www.w3.org/1999/02/22-rdf-syntax-ns#first>
<http://pop.h-cdn.co/assets/cm/15/05/54ca9daa9cd6d_-_space_plane_shuttle_md-28662836.jpg>
<http://www.popularmechanics.com/space/a5448/behind-the-air-forces-secret-robotic-space-plane/>