1. Centre of Low Temperature Physics of SAS and P.J. Šafárik University, Park Angelinum 9, 04001 Košice, Slovak Republic
2. Institute of Inorganic Chemistry, FCHPT, Slovak University of Technology, 812 37 Bratislava, Slovakia
3. Department of Chemistry, FPV, University of SS Cyril and Methodius, 917 01 Trnava, Slovakia