D. Wybranowski, “Natural conditions as an one factor belonging to war campaigns in Thietmar’s and Gallus Anonymous’s narration. Appendix to first Piast’s policy”, in Armia kontra natura, vol. 2, T. Grabarczyk and M. Pogońska-Pol, Eds. Poland: Lodz University Press, 2020, pp. 81–120. doi: 10.18778/8220-057-7.05.