 Complete the following phrase:  From 1921 to 1991, the city formed part of the Ukrainian Soviet Socialist Republic, which became a founding republic of the Soviet Union in 1922. The major events that took place in Soviet Ukraine during the interwar period all affected Kyiv: the 1920s Ukrainization as well as the migration of the rural Ukrainophone population made the Russophone city Ukrainian-speaking and bolstered the development of Ukrainian cultural life in the city; the Soviet Industrialization that started in the late 1920s turned the city, a former centre of commerce and religion, into a major industrial, technological and scientific centre; the 