A referendum concerning the extension of the period between general elections for the legislative assembly from 3 years to 4 years was put to New South Wales voters on 19 September 1981, the same day as the state election. The extension was approved by voters.
The text of the question was:
Do you approve a Bill for an Act to extend the maximum period between general elections for the Legislative Assembly from 3 years to 4 years?
References
New South Wales referendum, 1981 Wikipedia(Text) CC BY-SA