Holocene &amp; Historic range map of the two European bison species (Bison bonasus and Bison priscus): Holocene (B. priscus only) in light green; B. bonasus range in the high middle ages in dark green, relict B. bonasus populations in the 20th century in red   Holocene range  Historical range  Relict populations in the 20th century
References: 

Norbert Benecke. The Holocene distribution of European bison - the archaeozoological record. Munibe (Antropologia_Arkeologia) 57 421-428 2005. ISSN 1132_2217. Refers to Liljegren R. and Ekstrom J., 1996. The terrestrial late Glacial fauna in south Sweden. In L. Larsson (Hrsg). The earliest settlement of Scandinavia and its relationship with neighbouring areas. Acta Archaeologica Lundensia 8, 24, 135-139, Stockholm.
Markova, A.K., et al., Changes in the Eurasian distribution of the musk ox (Ovibos moschatus) and the extinct bison (Bison priscus) during the last 50 ka BP, Quaternary International (2015), https://dx.doi.org/10.1016/j.quaint.2015.01.02 https://www.researchgate.net/publication/275412500_Changes_in_the_Eurasian_distribution_of_the_musk_ox_Ovibos_moschatus_and_the_extinct_bison_Bison_priscus_during_the_last_50_ka_BP
M. Tokarska, C. Pertoldi, R. Kowalczuk, K. Perzanowski. Genetic status of the European bison Bison bonasus after extinction in the wild and subsequent recovery. Mammal Review, January 2011.
Bunzel-Drüke, Finck, Kämmer, Luick, Reisinger, Riecken, Riedl, Scharf &amp; Zimball: "Wilde Weiden: Praxisleitfaden für Ganzjahresbeweidung in Naturschutz und Landschaftsentwicklung. Arbeitsgemeinschaft Biologischer Umweltschutz im Kreis Soest e.V. (ABU), 2008. ISBN 978-3-00-024385-1
Sipko, T., P. (2009). European bison in Russia – past, present and future. European Bison Conservation Newsletter Vol 2, pp: 148–159
Own work
Leonid 2