1. Department of Theoretical Physics and Astrophycis, Masaryk University, Kotlářská 2, 611 37 Brno, Czech Republic
2. Astronomical Institue of the Czech Academy of Sciences, Fričova 298, 251 65 Ondřejov, Czech Republic
3. Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität at Heidelberg, Mönchhofstr. 12-14, D-69120 Heidelberg, Germany
4. Konkoly Observatory, Konkoly Thege Miklós út 15-17, H-1121 Budapest, Hungary