![]() | ![]() |
Astron. Astrophys. 342, 763-772 (1999) AcknowledgementsThe author would like to thank the referee Dr. P. Hartigan for his helpful comments that improved the clarity of the paper and Dr. C. Ceccarelli for her careful english revision of the paper and helpful discussions. ![]() ![]() ![]() ![]() © European Southern Observatory (ESO) 1999 Online publication: February 23, 1999 ![]() |