Andrzej Slaczka, Adam Wasilczyk (2017). ULTRA CLEAN COAL FROM POLISH COAL DEPOSITS. SGEM International Multidisciplinary Scientific GeoConference EXPO Proceedings; 17th International Multidisciplinary Scientific GeoConference SGEM2017, Energy and Clean Technologies, 659-666. https://doi.org/10.5593/sgem2017/42/s17.082