1. Astronomical Institute, University of Wrocław, Kopernika 11, PL-51-622 Wrocław, Poland
2. Astronomical Observatory, University of Warsaw, Al. Ujazdowskie 4, PL-00-478 Warsaw, Poland
3. Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, Bartycka 18, PL-00-716 Warsaw, Poland
4. Centre de Recherche en Astrophysique du Québec, Dépt. de physique, Univ. de Montréal, C.P. 6128, Succ. C-V., Montréal, QC, H3C 3J7, Canada
5. American Association of Variable Star Observers, 49 Bay State Road, Cambridge, MA 02138, USA
6. Department of Electronics, Electrical Engineering and Microelectronics, Silesian University of Technology, Akademicka 16, PL-44-100 Gliwice, Poland
7. Department of Physics and Space Science, Royal Military College of Canada, PO Box 17000, Station Forces, Kingston, ON K7K 0C6, Canada
8. Institut für Astro- und Teilchenphysik, Universität Innsbruck, Technikerstraße 25, A-6020 Innsbruck, Austria