<https://rainguard.com/2018/08/30/choosing-the-right-formula/rtu-vs-conc-blog-image/>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<https://rainguard.com/2018/08/30/choosing-the-right-formula/rtu-vs-conc-blog-image/>