<https://secure.gravatar.com/avatar/54735c832f965b2b48a7d71725991681?s=96&amp;d=mm&amp;r=g>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<https://www.borsainside.com/mercati_usa/57074-chiusura-in-negativo-per-i-prezzi-del-petrolio/>