1. Slovak Academy of Sciences; Institute of Materials Research; Watsonova 47 040 01 Kosice Slovakia
2. Faculty of Mining, Ecology, Process Control and Geotechnology; Technical University of Kosice; Letna 9 042 00 Kosice Slovakia
3. Bulgarian Academy of Sciences; Institute of Catalysis; Acad. G. Bonchev St BU-1113 Sofia Bulgaria