We thank to the staff of IUE (M. Barylak) and HST for providing us with the archive data, A. Antalová, S. Balman, J. Gallagher, R. Hjellming, M. Livio, H. Lloyd, T. O'Brien, M. Saniga, A. Skopal, A. Scott for stimulating discussions and M. Bode for reading the manuscript and valuable comments. We express our sincere gratitude to our referee H. W. Duerbeck for his fruitful suggestions, criticism and comments that substantially contributed to the improvement of the paper. The authors are obliged to the referee and to M. Varner for improvements of English. Special thanks belong to Mrs. G. Chocholová for generous financial support and interest in achieved results. This research has been partly supported through the Slovak Academy of Sciences Grant No. 1282/1995.
© European Southern Observatory (ESO) 1997
Online publication: July 3, 1998