Quorum requirements for a referendum to be valid

Nauru
Answer
No quorum requirements
Source
Neither the Constitutional Polls Act nor theConstitution itself sets any quorum.
Constitutionof Nauru
(adoptedin 31 January 1968, last amended in 17 May 1968)
http://www.naurugov.nr/parliament/constitution.html
ReferendumProcedures Act 2009
(adoptedin 27 November 2009)
http://aceproject.org/ero-en/regions/pacific/NR/nauru-referendum-procedures-act-2009/view