31 single stellar populations (solar-scaled isochrones) 32 single stellar populations (alpha-enhanced isochrones) 35 abundance pattern of M67 36 abundance pattern of CN-strong stars in 47 Tuc, adopting the solar-scaled Padova isochrones by Girardi et al. (2000A&AS..141..371G), and a dwarf-poor IMF (x=-4) 37 abundance pattern of CN-weak stars in 47 Tuc, adopting the solar-scaled Padova isochrones by Girardi et al. (2000A&AS..141..371G), and a dwarf-poor IMF (x=-4) 38 (CN-strong) abundance pattern of NGC 6528, adopting the solar-scaled Padova isochrones by Girardi et al. (2000A&AS..141..371G) and a Salpeter IMF