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Astron. Astrophys. 351, 607-618 (1999) AcknowledgementsWe are very indebted to R. Hudec who has put Sonneberg 1928-1982 data at our disposal. The work was partially supported by NFSR under project No. 715/97.
© European Southern Observatory (ESO) 1999 Online publication: November 3, 1999 ![]() |