[1] Institut für Astronomie, Universität Wien, Türkenschanzstrasse 17, Wien,A-l 180, Austria
[2] Instituto de Astrofísica de Andalucia, Apt. 2144, Granada,E-18080, Spain
[3] King's College, 10766-97 Street, Edmonton,AB, Canada
[4] Konkoly Observatory, Box 67, Budapest XII,H-1525, Hungary
[5] Beijing Observatory, Academy of Sciences, Beijing, China