Quorum requirements for a referendum to be valid

Philippines
Answer
Not specified by legislation
Source
1987 CONSTITUTION OF THE REPUBLIC OF THE PHILIPPINES
http://www.chanrobles.com/philsupremelaw1.htm
Republic Act No. 6735 'TheInitiative and Referendum Act'
http://www.chanrobles.com/republicactno6735.htm#.UMhZ8Gd32uI
Republic Act No. 6735'The Initiative and Referendum Act'