HASSELKUS, Hans, and Andreas REITZE. “Sonar Surveying of Caverns and 3D Modelling of Entire Cavern Fields”. Geology, Geophysics and Environment 38, no. 2 (April 1, 2012): 251. Accessed January 18, 2025. https://ggae.agh.edu.pl/index.php/geol/article/view/210.