<https://pregel.it/el/%ce%b1%cf%81%cf%87%ce%b9%ce%ba%ce%ae-%cf%83%ce%b5%ce%bb%ce%af%ce%b4%ce%b1/#organization>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<https://pregel.it/el/%CE%BD%CE%AD%CE%B1/>