Legal provisions for optional referendums at national level

The Constitution of the Republic of Mali (1991)http://confinder.richmond.edu/admin/docs/Mali.pdf

Article 41: The President of the Republic, by proposal of the Cabinet, during the duration of its sessionsor by proposal of the National Assembly, after the opinion of the Constitutional Court is published in the Official Journal, may place under referendum any and all questions of national interest, any law related to the organization of public powers, consisting of an approval of an accord of union or an authorization of a treaty which, without being unconstitutional, would have effect on the function of the Institutions. [...]