Foe of Iran government calls for referendum, The New York Times (2010)
Mehdi Karroubi, one of the most prominent opposition leaders, calls for a referendum. Without specifying the precise questions, he said the referendum would be about free elections and limitations of the powers of the Guardian Council. Taken as a symbolic gesture by several analysts, this step is considered as a form of psychological pressure on the Iranian leaders.
The link address is: http://www.nytimes.com/2010/02/23/world/middleeast/23karroubi.html