Two sets of observational carbon stellar yields for low-and-intermediate mass
stars are computed from planetary nebulae abundances derived from C II
λ4267 and C III λλ1906+1909 lines, respectively. By
comparing C/O values observed in stars of the solar vicinity and Galactic HII
regions with those predicted by chemical evolution models for the Galaxy, which
assume these observational yields, I conclude that the C abundances derived
from permitted lines are better than those derived from forbidden lines.Comment: 2 pages, Proceedings of the conference "Ionized Gaseous Nebulae", Nov
21-24, 2000; RevMexAA in pres