Observational Properties of Primordial Stellar Populations
  We present the first results of a study of the expected properties of the first stellar generations in the Universe. In particular, we consider and discuss a series of properties that, on the basis of the emission from associated HII regions, permit one to discern {\it bona fide} primeval stellar generations from the ones formed after pollution from supernova explosions. The expected performance of NGST for the study and the characterization of primordial sources is also discussed. 
N. Panagia (ESA/STScI), M. Stiavelli, H.C. Ferguson, and H.S. Stockman   (STScI)