1. Department of Physics and Institute of Theoretical and Computational Physics, University of Crete, 71003 Heraklion, Greece
2. Foundation for Research and Technology – Hellas, IESL, Voutes, 71110 Heraklion, Greece
3. Department of Materials Science and Technology, University of Crete, 71003 Heraklion, Greece
4. Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, Bartycka 18, PL-00-716 Warszawa, Poland
5. University of California, San Diego, Center for Astrophysics and Space Sciences, 9500 Gilman Dr., La Jolla, CA 92093-0424, USA
6. Department of Physics and Astronomy, The University of Southampton, Southampton SO17 1BJ, UK