<https://secure.gravatar.com/avatar/9a21166ea44a09382699c001a1595b86?s=96&amp;d=mm&amp;r=g>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<https://www.etutorworld.com/blog/the-princeton-review-vs-etutorworld-com/>