Issues in relation to which referendums are mandatory at the national level

Iraq
Answer
Constitutional amendments
Source
Constitution (2005)
http://parliament.iq/manshurat/dastoreng.pdf
Article 142: [?]Third: The articles amended by the Council of Representatives pursuant to item ?Second? of this Article shall be presented to the people for voting on them in a referendum within a period not exceeding two months from the date of their approval by the Council of Representatives.