Legal provisions for mandatory referendums at national level

Peru
Political Constitution of Peru (Constitución Política del Per?)
http://aceproject.org/ero-en/regions/americas/PE/peru-constitution-as-amended-to-1993-english/view
Article 206
Any initiative of constitutionalreform must be adopted by Congress with the vote of the
absolute majority of the legalnumber of its Members and said reform must be ratified
by a referendum. The referendummay be exempted when the consent of Congress is
obtained in two successiveregular sessions with a favorable vote, in each case, greater
than two-thirds of the legalnumber of Members of Congress. A law concerning a
constitutional reform shall notbe objected by the President of the Republic.
The right to initiate aconstitutional reform corresponds to the President with the
approval of the Cabinet, toMembers of Congress; and to a number of citizens
equivalent to 0.3 percent of thevoting population, with their signatures being verified by
the correspondingelectoral authority.