On 30-31 March, 1979 a referendum was held in Iran to determine the political system of the country (Previously the monarchial regime had been overthrown on February 11, 1979).
But the problem with that referendum was that it was not standard. It just had one candidate (e.g. Islamic Republic) and people had to vote either yes or no to that single choice. In other words, other political systems that were representating many people weren't allowed to participate in the process so that the candidate remains the sole opponent of itself in the dictatorship. As a result, above 98% of the voters (with a turnout of above 90%) decided to say yes because there was a huge propaganda advocating the Islamic Republic and also it wasn't clear what would have happened next if they had chosen to say no. Also, the color of ballots (green for Yes, red for No) had a psychological impact on the voters.
My question: Is Iran alone? Are there any other countries besides Iran that have held a referendum to determine the political system of the country after the collapse of the previous one, but only with one choice available?
Update: I'm seeing answerers are making examples of constitutional bill referendums. While constitutional bill referendums do ratificate the political system of the country, it wasn't the case for Iranian referendum. They just asked people to ratificate the political system. A constitutional bill referendum took place in Iran in 1989 (10 years after the revolution). So I think Iran might be still alone in holding a referndum to choose the political system, and a constitutional bill referendum so many years after it. In other countries these referendums are collected in one constitutional bill referendum.