1. 1. Silva MC: Research testing nursing theory: State of the art. Advances in Nursing Science 1986;9(1):1-11.
2. 2. Webster's New Twentieth Century Dictionary: New York Collins World. 1977.
3. 3. Walker LV Avant KC: Strategies for Theory Construction in Nursing. Connecticut Appleton-Century-Crofts. 1983.
4. 4. Schaie KW Geiwitz J: Adult Development and Aging. Boston. Little. Brown and Company 1982.
5. 5. Botwinick J Thompson LW: Practice of speeded response to age sex and set. J Gerontol 1967; 22:72-76.