Who can initiate an optional referendum at the national level?

Constitution 1996

http://www.assembly.gov.gm/index.php?option=com_docman&task=cat_view&Itemid=88&gid=49&orderby=dmdate_published&ascdesc=DESC

Article 102 (Optionalreferendum)

In additionto the other powers conferred on the National Assembly by this Constitution orany other law, the National Assembly may-

   (d) include in a Bill a proposal for areferendum on an issue of national concern defined in the Bill, or