1. European Commission. Confronting Demographic Change: a new solidarity between the generations. The Green Paper on Demographic Changes. Brussels, EC; 2005.
2. World Health Organization. Active ageing: a policy framework. Geneva: WHO; 2002.
3. Laslett P. A fresh map of life: the emergence of the third age. Cambridge: Harvard University Press; 1989.
4. Kalache A, Barreto SM, Keller I. Global ageing: the demographic revolution in all cultures and societies. In: Johnson ML, ed. The Cambridge handbook of age and ageing. Cambridge: Cambridge University Press; 2005.
5. Smith J. The Fourth Age: a period of psychological mortality. Berlin: Max Planck Institute for Human Development; 2001.