1. Faculty of Physics
2. Vilnius University
3. LT-10222 Vilnius
4. Lithuania
5. Department of Physics
6. Paderborn University
7. D-33098 Paderborn
8. Germany
9. Institute of Low Temperature and Structure Research
10. Polish Academy of Sciences
11. PL-50-950 Wroclaw 2
12. Poland
13. Felix Bloch Institute for Solid State Physics
14. Leipzig University
15. D-04103 Leipzig