The Socialist Republic of Macedonia, or SR Macedonia, commonly referred to as Socialist Macedonia, Yugoslav Macedonia or simply Macedonia, was one of the six constituent republics of the post-World War II Socialist Federal Republic of Yugoslavia. After the transition of the political system to parliamentary democracy in 1990, the Republic changed its official name to Republic of Macedonia in 1991, and with the beginning of the breakup of Yugoslavia, it declared itself an independent country and held a referendum on 8 September 1991 on which a sovereign and independent state of Macedonia, with a right to enter into any alliance with sovereign states of Yugoslavia was approved.