Quorum requirements for a referendum to be valid

Serbia
Serbia, Law on the Referendum and the People’s Initiative (December 2021) [in Serbian], accessed 20 December 2021
Adoption and Legal Effect of a Decision in a Binding Referendum
Article 11. In a binding referendum, a decision shall be adopted if the majority of citizens who participated in the referendum in the territory on which the referendum was called have voted for it.
The decision referred to in paragraph 1 of this Article shall have legal effect from the day of declaration of the overall results of the referendum.
Establishment of Opinion in a Consultative Referendum
Article 12. In a consultative referendum, the opinion of citizens shall be established by the vote of the majority of citizens who participated in the referendum, and it shall not be legally binding.