Who can initiate an optional referendum at the national level?

Costa Rica
- President
- Legislative majority
- Registered electors
Political Constitution of Costa Rica (ConstituciónPolítica de la República de Costa Rica). Article 105.
http://aceproject.org/ero-en/regions/americas/CR/costa-rica-constitucion-politica-de-la-republica
The President can only initiate if it is backed by amajority of the members of Legislative; and those initiated by the Legislativerequire the adherence of two thirds of its members.