<https://secure.gravatar.com/avatar/8ce16cac7a7919043516b0caac304558?s=96&amp;d=mm&amp;r=g>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<https://www.doublesmart.nl/doelen-stellen-en-conversie-meten/>