Legal provisions for mandatory referendums at national level

Liberia
Constitution of the Republic of Liberia
(Adopted in January 1986)
http://www.liberianlegal.com/constitution1986.htm#_THE_LEGISLATURE
Article 91.
This Constitution may be amended whenevera proposal by either (1) two-thirds of the membership of both Houses of theLegislature or (2) a petition submitted to the Legislature, by not fewer than10,000 citizens which receives the concurrence of two-thirds of the membershipof both Houses of the Legislature, is ratified by two-thirds of the registered voters,voting in a referendum conducted by the Elections Commission not sooner thanone year after the action of the Legislature.
Article 91 of the Constitution provides for both mandatoryreferendum and citizen initiative. When a constitutional amendment is proposedby 2/3 of both house of the legislation, it undergoes a mandatory referendum.Citizen initiative process is triggered when a constitutional amendment is proposedby citizens through a petition of 10,000 or more in concurrence with 2/3 ofapproval of both Houses of the Legislature.