http://wp.unil.ch/space/files/2016/05/SPACE-I-2014-Report_final.1.pdf
http://www.lastampa.it/2016/06/27/italia/politica/rodot-quando-i-referendum-diventano-un-boomerang-JuXpMSRHAkJH5mE0mawMrL/pagina.html
http://www.oecd-ilibrary.org/docserver/download/5jlv2jhfnt48-en.pdf?expires=1494939516&id=id&accname=guest&checksum=08592067325A17BFB82AC6F6E15110B2