Quorum requirements for a referendum to be valid

Constitution of Croatia 2010, Article 87

[...] At such referenda, decisions shall be made by a majority of voters taking part therein.

"It was obvious to the vast majority of Croatian politicians and constitutional scholars that the approval quorum required for referendums on state alliances is too high a barrier and that it could be the greatest obstacle in the process of Croatia’s accession to the EU, considering that this organisation is a union of states of sorts (and not simply an international organisation). It was due to this that the Constitution was amended in 2010 and (amongst other changes) all quorums prescribed for the validity of referendum decisions were deleted. The intention of the constitution makers was only to facilitate the decision on the future EU membership referendum, but the consequences have been much larger. It is important to state that it is now much easier to reach any decision in a state referendum, even to amend the Constitution itself, by a simple decision of the majority of the votes cast."  Source