<https://www.minilabhelp.com/index.php?/forums/topic/26742-difference-from-an-s2-s4/#comment-66224>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<https://www.minilabhelp.com/index.php?/forums/topic/26742-difference-from-an-s2-s4/&tab=comments#comment-66224>