<http://www.w3.org/1999/02/22-rdf-syntax-ns#first>
<http://pop.h-cdn.co/assets/cm/15/05/54caabfa3f306_-_water-heater-3-sm.jpg>
<http://www.popularmechanics.com/home/how-to/a6010/tankless-water-heater-how-it-works/>