<http://www.w3.org/1999/02/22-rdf-syntax-ns#first>
<http://pop.h-cdn.co/assets/cm/15/06/640x320/54cfcd7b63b8c_-_pulse_jet_0311-de.jpg>
<http://www.popularmechanics.com/home/how-to-plans/how-to/a6549/how-to-build-a-pulse-jet/>