Re: Curious Spanish attitude
That one's easy. Articles 167 and 168 of the referendum. The official English translation is at http://www.congreso.es/constitucion/ficheros/c78/cons_ingl.pdf , but in short: a handful of articles get special protection by automatically requiring amendments to be approved by referendum. The majority can be amended by a supermajority in parliament, but must be referred to the people if 10% of either house of parliament votes to require that.