1. Department of Nuclear Physics and Biophysics, Faculty of Mathematics, Physics and Informatics, Comenius University, Mlynská Dolina F-1, 841 04 Bratislava, Slovak Republic
2. Laboratory of Radiometric Expertise, Institute of Nuclear Physics PAN (IFJ PAN), Radzikowskiego 152, Krakow 31-342, Poland
3. Institute of Radiochemistry and Radioecology, University of Pannonia, Egyetem Str. 10, Veszprém 8200, Hungary
4. RADON v.o.s., Novakovych 6, 180 00 Praha 8, Czech Republic
5. Geophysical Institute, Slovak Academy of Sciences, Dúbravská Cesta 9, 845 28 Bratislava, Slovak Republic