^Brzechczyn, Krzysztof (2009), Idealization XIII: Modeling in History. Amsterdam: Rodopi. ISBN9789042028319.
^Davies, Norman (2003), God's Playground A History of Poland: Volume 1: The Origins to 1795. Oxford: Oxford University Press. ISBN9780199253395.
^Topolski, Jerzy (1976), Methodology of History.Warsaw: PWN – Polish Scientific Publishers in Jaakko Hintikka, Synthese Library. Boston: D.Reidel Publishing Company. ISBN978-94-010-1125-9
^"The main tribe inhabiting the reaches of the Upper Vistula and its tributaries was the Vislane (Wislanie) who, by the mid-ninth century were considered by the neighbouring Moravians as "very powerful" The expansionist policy of the Christian Moravian state led to eventual conflict with the pogan Vislane. ending in the defeat of the latter and their annexation to the Great Moravian Empire between Ad 875-879" . [in:] Trade and urban development in Poland: an economic geography of Cracow. Francis W. Carter. P. 46. 1994 op. cit. L. Hajdukiewicz and M. Karaś. The Jagiellonian University: Traditions, The Present, The Future. Cracow. 1978, p. 17.