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On December 30, 1922, the First Congress of the Soviets of the USSR approved the Treaty on the Creation of the USSR, by which Russia was united with the Ukrainian Soviet Socialist Republic, Byelorussian Soviet Socialist Republic, and Transcaucasian Soviet Federal Socialist Republic into a single federal state, the Soviet Union. Later treaty was included in the 1924 Soviet Constitution,[clarification needed] adopted on January 31, 1924 by the Second Congress of Soviets of the USSR.

Along with the Ukrainian Soviet Socialist Republic and Byelorussian Soviet Socialist Republic, what state joined Russia to form the Soviet Union?
Transcaucasian Soviet Federal Socialist Republic