<http://www.w3.org/1999/02/22-rdf-syntax-ns#rest>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#nil>
<http://www.popularmechanics.com/science/health/a8289/as-shortage-worsens-we-visit-the-federal-helium-reserve-14720528/?click=pm_latest>