"Not too old" metal deficient stellar populations: the case of   metallicity Z=0.00001
  We investigate the evolution of metal deficient stellar structures, presenting H-burning isochrones covering cluster ages from 800 Myr to 7 Gyr. Evolutionary evidences for selection effects in the metallicity distribution of very metal poor H-burning red giants are reported. The evolution of stars during central and shell He burning is further investigated, discussing the occurrence of He burning pulsators as a function of cluster age. 
S. Cassisi (Osservatorio Astronomico Collurania, Teramo; Universita'   de l'Aquila), M. Castellani (Universita' di Roma "La ...