1. 1) World Health Organization (WHO): The first ten years of the World Health Organization. World Health Organization, Geneva, 1958.
2. 2) WHO Scientific Group on the Epidemiology of Aging: The use of epidemiology in the study of the elderly (Technical report series No. 706). World Health Organization, Geneva, 1984.
3. 3) Lawton MP: Assessing the competence of older people. In: Kent DP, Kastenbaum R, Sherwood S (eds), Research planning and action for the Elderly: The power and potential of social science. Human Science Press, New York, 1972; 122-143.
4. 4) Katz S: Assessing self-maintenance: Activities of daily living, mobility, and instrumental activities of daily living. J Am Geriatr Soc 1983; 31: 721-727.
5. 5) Lawton MP, Brody EM: Assessment of older people: Self-maintaining and instrumental activities of daily living. Gerontologist 1969; 9: 179-186.