Abstract
We present a review about the relevance of the paper by M. Peimbert and R. Costero, 1969, BOTT, 5, 31, 3, on the chemical abundance determinations of H II regions. We analize the observational evidence in favor of the presence of temperature variations inside gaseous nebulae. We make a brief mention of the methods used to estimate the contribution of the unobserved ions to the total chemical abundances.
