1. Institute of Physics, Nicolaus Copernicus University, Grudziądzka 5/7, 87-600 Toruń, Poland
2. Physics Department, Trento University, Sommarive 14, 38050 Trento, Italy
3. Institute of Physics, Pomeranian Pedagogical Academy, 76-200 Słupsk, Poland
4. CNR-INFM BEC Center, 38050 Trento Italy
5. Center of Theoretical Physics, Polish Academy of Sciences, al. Lotników 32/46, 02-668 Warszawa, Poland
6. Institute of Fluid Flow Machinery, Polish Academy of Sciences, Fishera 14, 80-952 Gdańsk, Poland