1. Institute of Mineral and Waste Processing, Waste Disposal and Geomechanics, Technical University-Clausthal, Walther-Nernst 9, Clausthal, Germany
2. Institute of Geotechnics, Slovak Academy of Sciences, Watsonova 45, Košice, Slovakia
3. Institute of Catalysis, Bulgarian Academy of Sciences, Acad. Georgi Bonchev 11, Sofia, Bulgaria
4. Faculty of Mining, Ecology, Process Control and Geotechnology, Technical University-Košice, Letná 9, Košice, Slovakia