1. Astronomical Institute University of Wrocław, Kopernika 11, PL-51-622 Wrocław, Poland
2. Nicolaus Copernicus Astronomical Center Polish Academy of Sciences, Bartycka 18, PL-00-716 Warsaw, Poland
3. Dépt. de physique, Univ. De Montréal, C.P. 6128, Succ. Centre-Ville, and Centre de Recherche en Astrophysique du Québec, Montréal, QC H3C 3J7, Canada
4. AAVSO, 49 Bay State Rd. Cambridge, MA 02138, USA
5. Institute of Automatic Control, Silesian University of Technology, Akademicka 16, PL-44-100 Gliwice, Poland
6. Department of Physics & Space Science, Royal Military College of Canada, PO Box 17000 Station Forces, Kingston, ON K7K 0C6, Canada
7. Institute for Astrophysics, University of Vienna, Tuerkenschanzstrasse 17, A-1180 Vienna, Austria
8. Institut für Astro- und Teilchenphysik, Universität Innsbruck,Technikerstrasse 25/8, A-6020 Innsbruck, Austria