MAKOBA, Mmoloki, et al. “CHARACTERIZATION OF BOTSWANA COAL FROM TWO COAL FIELDS: MABESEKWA AND MMAMABULA TO DETERMINE ITS COAL RANK”. Studia Universitatis Babeș-Bolyai Chemia, vol. 65, no. 2, June 2020, pp. 243-56, doi:10.24193/subbchem.2020.2.20.