825 Heads of State or Government Awarded a Nobel Prize [ EB/ OL ]. http : //www. nobelprize, org/nobel _ prizes/presidents - nobel- prize, html, 2015 -08 - 19.
9List of Presidents of the United States [ EB/OL ]. http : /! en. wikipedia, org/wiki/List of Presidents of the_ United_ States, 2015 - 08 - 19.
