  We investigate techniques that can be used to determine ages of recently star
forming regions during the phase dominated in the near-IR by the asymptotic
giant branch stars (10^8-10^9 yrs). In particular, we present selected near-IR
spectroscopic features that identify the contribution of O-rich and C-rich AGB
variable stars to the integrated spectra of post-starbursts. The observational
strategy based on those features is presented. We discuss the robustness of our
selected features in constraining the ages of the post-starburst population
depending on its physical environment and on underlying evolved populations.
The interplay between the integrated features of populations and the stellar
parameters is discussed.
