On October 28, 1989, the Ukrainian Supreme Soviet decreed that effective January 1, 1990, Ukrainian would be the official language of Ukraine, while Russian would be used for communication between ethnic groups. On the same day The Congregation of the Church of the Transfiguration in Lviv left the Russian Orthodox Church and proclaimed itself the Ukrainian Greek Catholic Church. The following day, thousands attended a memorial service at Demianiv Laz, and a temporary marker was placed to indicate that a monument to the "victims of the repressions of 1939–1941" soon would be erected.

What was made Ukraine's official language in 1990?