Supreme Soviet of USSR, Concerning the procedure of secession of a Soviet Republic from the Union of Soviet Socialist…
“ Decision of a Soviet Republic to secede from the USSR must be made by means of a referendum if so voted by not less than two-thirds of the citizens of the USSR, who permanently resided on the territory of the Republic and are eligible to vote in accordance with laws of the USSR by the time the decision was made to conduct a referendum on secession from the Soviet Union. ”
