Who drafts the referendum question?
Chile
PoliticalConstitution of Chile (Constitución Política de la República de Chile), article93.5 (attributions of the Constitutional Court);
http://aceproject.org/ero-en/regions/americas/CL/chile-constitucion-politica-de-la-republica-de
and
Law18.700 on the Constitutional Organization of Popular Voting and Counting (Ley18.700 Ley Orgánica Constitucional sobre Votaciones Populares y Escrutinios),article 26.