Analysis of information sources in references of the Wikipedia article "Grand Duchy of Lithuania" in English language version.
...he wrote to the Grand Duke of Lithuania, admonishing him to do everything in his power to persuade his consort to 'abjure the Russian religion, and accept the Christian Faith.'
The first coins, anonymous (Type I), roughly imitate Tatar coins of Jani beg struck in Gulistán in the years 1351–1353 (Kozubovs'kyi 1994). Kozubovs'kyi regarded them as the oldest coins of Volodymyr from the sixties to the early eighties but Khromov, while facing some recent finds ( or a find ) from the Sumy province, is of the opinion that they were struck earlier, between 1354–63 under the rule of the Ruirikid Prince Fiodor of Kiev, and that they were struck somewhere to the east of the capital town, in the Sumy region ( Khromov 2004, 2006 ).
{{citation}}: CS1 maint: postscript (link)Within the [Lithuanian] grand duchy the Ruthenian (Ukrainian and Belarusian) lands initially retained considerable autonomy. The pagan Lithuanians themselves were increasingly converting to Orthodoxy and assimilating into the Ruthenian culture. The grand duchy's administrative practices and legal system drew heavily on Slavic customs, and an official Ruthenian state language (also known as Rusyn) developed over time from the language used in Rus. Direct Polish rule in Ukraine in the 1340s and for two centuries thereafter was limited to Galicia. There, changes in such areas as administration, law, and land tenure proceeded more rapidly than in Ukrainian territories under Lithuania. However, Lithuania itself was soon drawn into the orbit of Poland following the dynastic linkage of the two states in 1385/86 and the baptism of the Lithuanians into the Latin (Roman Catholic) church.
Formally, Poland and Lithuania were to be distinct, equal components of the federation, [...] But Poland, which retained possession of the Lithuanian lands it had seized, had greater representation in the Diet and became the dominant partner.
While Poland and Lithuania would thereafter elect a joint sovereign and have a common parliament, the basic dual state structure was retained. Each continued to be administered separately and had its own law codes and armed forces. The joint commonwealth, however, provided an impetus for cultural Polonization of the Lithuanian nobility. By the end of the 17th century, it had virtually become indistinguishable from its Polish counterpart.