Parliamentary Assembly stated that the referendum violated international standards. Members of the opposition claimed that the organisation of the referendum involved several serious violations of legislation, including the constitution. History Early Middle Ages In the Iron Age, the south of present-day Belarus was inhabited by tribes belonging to the Milograd culture (7th-3rd century BC) and later Zarubintsy culture. They are mostly considered Balts. Since the beginning of common era, these lands were penetrated by the Slavs, a process that intensified during the migration period (4th century). A peculiar symbiosis of Baltic and Slavic cultures took place in the area, but it was not a fully peaceful process, as evidenced by numerous fires in Balts' settlements in the 7th-8th centuries. According to Russian archaeologist , it was intensive contacts with the Balts that contributed to the distinctiveness of the Belarusian tribes from the other Eastern Slavs. The Baltic population gradually became Slavic, undergoing assimilation, a process that for eastern and central Belarus ended around the 12th century. Belarusian lands in the 8th-9th centuries were inhabited by 3 tribal unions: the Krivichs, Dregoviches and Radimichs. Of these, the Krivichs played the most important role; Polotsk, founded by them, was the most important cultural and political center during this period. The principalities formed at that time on the territory of Belarus were part of Kievan Rus'. The process of the beginning of the East Slavic linguistic community and the separation of Belarusian dialects slowly took place. In the Grand Duchy of Lithuania As a result of Lithuanian expansion, the lands of Belarus became part of the Grand Duchy of Lithuania. This fact accelerated the Slavicization of the Baltic population. Also, the rulers and the elite of the Grand Duchy adopted elements of Ruthenian culture, primarily Old Belarusian language, which became the main language of writing. Belarusians began to emerge as a nationality during the 13th and 14th centuries in the Grand Duchy of Lithuania mostly on the lands of the upper basins of Neman River, Dnieper River, and the Western Dvina River. The Belarusian people trace their distinct culture to the Grand Duchy of Lithuania, earlier Kievan Rus' and the Principality of Polotsk. Litvin was a term used to describe all residents of the Grand Duchy of Lithuania, primarily those belonging to the noble state, without distinction of ethnicity or religion. At the same time, the term Ruthenian (Rusyn) was in use, referring