Kotzebue, August Friedrich Ferdinand von (1761-1819). Switrigailo, Grand Duke of Lithuania, or Supplement to the stories of Lithuanian, Russian, Polish and Prussian. St. Petersburg: in the printing house of the Medical Department of the Ministry of Internal Affairs, 1835.
Popov, Neil Alexandrovich (1833-1891). On the importance of Germanic and Byzantine influence on Russian historical life in the first two centuries of its development. Moscow: At the University Printing House Katkov and Co., 1871.