<http://www.w3.org/1999/02/22-rdf-syntax-ns#first>
<http://pop.h-cdn.co/assets/cm/15/06/768x516/54cfcfe49bedf_-_science_mysteries_03_0111-xl.jpg>
<http://www.popularmechanics.com/science/g137/sciences-greatest-unsolved-mysteries-progress-report/>