1. Asian Development Bank. (1997). Emerging Asia: Changes and challenges. Manila, Indonesia, Philippines: Asian Development Bank.
2. Atchley, R. C. (1989). A continuity theory of normal aging. The Gerontologist, 29(2), 183-190.
3. Black, B., & Kovacs, P. J. (1999). Age-related variation in roles performed by hospice volunteers. The Journal of Applied Gerontology, 18, 479-497.
4. Brim, O. G., & Ryff, C. D. (1980). On the properties of life events. In P. B. Balters & O. G. Brim (Eds.), Life span development and behavior (Vol. III, pp. 367-388). New York: Academic Press.
5. Cheng, S. H. (1991). Economic change and industrialization. In E. C. T. Chew & E. Lee (Eds.), A history of Singapore (pp. 182-215). Singapore: Oxford University Press.