Issues in relation to which referendums are mandatory at the national level

PoliticalConstitution of Brazil (Constituição da República Federativa do Brasil)

http://aceproject.org/ero-en/regions/americas/BR/brazil-constitution-2012

Direct Democracy Law (Lei N. 9.709)

http://aceproject.org/ero-en/regions/americas/BR/Brasil-Lei-N.-9.709-2012