Dzięgiel, Maciej. 2021. “The Geotouristic Attractiveness of the Underground Trails in Zabrze, Dąbrowa Górnicza and Tarnowskie Góry Towns (Silesian Upland)”. Geotourism/Geoturystyka 17 (1-2(60-61):23-38. https://doi.org/10.7494/geotour.2020.1-2(60-61).23.