Nikiforova, Aleksandra Aleksandrovna, and Maria E. Fleis. “A Universal Soil Classification System from the Perspective of the General Theory of Classification: A Review”. Bulletin of Geography. Physical Geography Series, no. 14 (May 18, 2018): 5–13. Accessed July 18, 2024. https://apcz.umk.pl/BOGPGS/article/view/16091.