Stellar Populations: High Spectral Resolution Libraries. Improved TP-AGB Treatment

I present a short description of the STELIB, HNGSL, IndoUS, MILES, ELODIE, UVES-POP, and IRTF libraries of empirical stellar spectra and show some applications of their use in population synthesis models. When new calculations of the TP-AGB evolutionary phase for stars of different mass and metallicity are included in population synthesis models, the stellar mass in galaxies at z from 1 to 3 determined from spectro-photometric data can be up to 50% lower than the mass determined from the BC03 models. The ages inferred for these populations are considerably lower than the BC03 estimates.