Contents of Ecotoxic Elements in Polish Coking Bituminous Coals and in Products of CokingPiotr Burmistrz, Tadeusz Dziok, Dorota Makowska, Faustyna Wierońska and Andrzej StrugałaE3S Web Conf., 108 (2019) 02002DOI: https://doi.org/10.1051/e3sconf/201910802002