Jurkowska, Agata Anna, and Ewa Świerczewska-Gładysz. “Opoka – a Mysterious Carbonate-Siliceous Rock: An Overview of General Concepts”. Geology, Geophysics and Environment 48, no. 3 (November 7, 2022): 257–278. Accessed April 18, 2025. https://journals.agh.edu.pl/geol/article/view/4968.