<http://www.w3.org/1999/02/22-rdf-syntax-ns#first>
<http://pop.h-cdn.co/assets/cm/15/05/480x360/54cb31d20ad29_-_tree-houses-06-0414-de.jpg>
<http://www.popularmechanics.com/technology/design/g1488/6-wooden-buildings-reaching-new-heights/>