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

Belarus
Constitution2004
https://www.constituteproject.org/constitution/Belarus_2004.pdf
Article140
TheConstitution, laws on amendments and addenda thereto, on the entry into forceof the said laws and instruments on the interpretation of the Constitutionshall be deemed to have been adopted where no less than two-thirds of theelected deputies of both chambers of the Parliament have voted in favor ofthem.
TheConstitution may be amended or supplemented via a referendum. A decision toamend or supplement the Constitution by means of a referendum shall be deemedadopted where a majority of citizens on the electoral roll have voted in favorof it.
ELECTORAL CODE OF THE REPUBLIC OF BELARUS (withamendments in 2011)
ElectoralCode of the Republic of Belarus
Article112. Questions Offered to the Referendum
Thequestions, which may be submitted to a republican referendum, shall include thequestions of utmost importance pertaining to the state and public life of theRepublic of Belarus.
Thequestions, which may be submitted to a local referendum, shall include thequestions of utmost importance for the population of respective territorialadministrative units, which fall within the competence of the respective localCouncils of Deputies, and executive and administrative bodies.
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