Quorum requirements for a referendum to be valid

Slovakia
Answer
- Mandatory referendum - turnout quorum
- Optional referendum - turnout quorum
Source
CONSTITUTIONOF THE SLOVAK REPUBLIC
(Adopted 1992; lastamended 2006)
http://www.nrsr.sk/web/default.aspx?SectionId=124
Chapter5: Legislative Power
Part2: The Referendum
Article 98
(1) Theresults of the referendum are valid if more than one-half of eligible votersparticipated in it and if the decision was endorsed by more than one half ofthe participants in the referendum.
Comment
All referendums - 50% of electorate