1. ABELIN Th., SCHLETTWEIN-GSELL D., KLEIN M.: Erhebung über Behinderungen und Bedürfnisse der Betagten in der Schweiz. Akt. Gerontol., 9, 83–86 (1979).
2. MADDOX G.L., DOUGLASS E.B.: Self-assessment of health: a longitudinal study of elderly subjects. J. Hlth. Soc. Behav., 14, 87–93 (1973).
3. NIE N.H. et al: Statistical package for the social sciences (2nd ed). New-York, McGraw Hill (1975).
4. ROSOW I., BRESLAU N.: A Guttman health scale for the aged. J. Geront., 21, 556–559 (1966).
5. WILLIAMS R.G.A., JOHNSTON M., WILLIS L.A. and BENNETT A.E.: Disability: a model and measurement technique. Brit. J. Prev. Soc., 30, 71–78 (1976).