Wybranowski, Dariusz. “Natural Conditions As an One Factor Belonging to War Campaigns in Thietmar’s and Gallus Anonymous’s Narration. Appendix to First Piast’s Policy”. Armia Kontra Natura, edited by Tadeusz Grabarczyk and Magdalena Pogońska-Pol, vol. 2, Lodz University Press, 2020, pp. 81-120, https://doi.org/10.18778/8220-057-7.05.