1. Mines Restructuring Company (Spółka Restrukturyzacji Kopalń S.A.), 41-914 Bytom, Poland
2. Department of Safety Engineering, Silesian University of Technology, 44-100 Gliwice, Poland
3. Faculty of Economics and Management, Opole University of Technology, 45-758 Opole, Poland
4. Biomass Energy Engineering Research Centre, School of Agriculture and Biology, Shanghai Jiao Tong University (SJTU), 800 Dongchuan Road, Shanghai 200240, China
5. Department of Resources and Environment, School of Agriculture and Biology, Shanghai Jiao Tong University (SJTU), 800 Dongchuan Road, Shanghai 200240, China
6. Central Mining Institute, 40-166 Katowice, Poland