<http://www.reddit.com/r/webdev/comments/2gypch/is_schemaorg_still_a_thing/>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<https://forum.edugorilla.com/forums/topic/what-approximate-value-should-come-in-place-the-of-question-mark-in-the-following-question-you-a-3/>