1. Department of Theoretical Physics, Institute of Physics, Maria Curie-Skłodowska University, pl. M. Curie-Skłodowskiej 1, 20-031 Lublin, Poland
2. Department of Physics, University of Tennessee, Knoxville, TN 37996, Knoxville, USA
3. Physics Division, Oak Ridge National Laboratory, P.O.Box 2008, Oak Ridge, TN 37831, USA
4. Institute of Theoretical Physics, Warsaw University, ul. Hoża 69, Warsaw, Poland