<https://secure.gravatar.com/avatar/657cf53a62ed373c88443786d5146c49?s=96&amp;d=mm&amp;r=g>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<https://www.learnamericanenglishonline.com/Blue%20Level/B10%20Articles.html>