<http://www.w3.org/1999/02/22-rdf-syntax-ns#first>
<http://pop.h-cdn.co/assets/cm/15/05/320x240/54cb2de2aacdd_-_sound-waves-03-0314-lgn.jpg>
<http://www.popularmechanics.com/military/g1458/7-amazing-things-you-can-do-with-sound-waves/>