1. Institute of Metal Science, Equipment and Technologies with Hydro- and Aerodynamics Centre “Acad. A. Balevski”, Bulgarian Academy of Sciences, Shipchenski Prohod Str., 67, 1574 Sofia, Bulgaria
2. Department of Chemistry, Technical University of Sofia, Kliment Ohridski Blvd., 8, 1000 Sofia, Bulgaria
3. Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Acad. Angel Bonchev Str., 11, 1113 Sofia, Bulgaria