G. Bertelli, A. Bressan and C. Chiosi are acknowledged for the many discussions and useful comments they made while the work was in progress. M.A.T. Groenewegen is acknowledged for suggestions afterwards. The referee M. Azzopardi is acknowledged for updating the author on the faint SMC and Fornax carbon stars. P. Marigo is thanked for patiently discussing with me the theoretical aspects of carbon star evolution. The research of Y.K. Ng is supported by TMR grant ERBFMRX-CT96-0086 from the European Community.
© European Southern Observatory (ESO) 1997
Online publication: March 24, 1998