 Complete the following phrase:  The Political Bureau of the Central Committee of the Communist Party of the Soviet Union or Politburo, ; abbreviated:  was the highest policy-making authority within the Communist Party of the Soviet Union. It was founded in October 1917, and refounded in March 1919, at the 8th Congress of the Bolshevik Party. It was known as the Presidium from 1952 to 1966. The existence of the Politburo ended in 1991 upon the 