1. Andrews, F., et al. (1973). Multiplication classification analysis. Ann Arbor, MI: University of Michigan Institute for Social Research.
2. Annas, J. (2004). Happiness as achievement. Daedalus, 133(2), 44–51.
3. Beneditt, T. (1974). Happiness. Philosophical Studies, 25, 1–20.
4. Bradburn, N. (1969). The structure of psychological well-being. Chicago: Aldine.
5. Bradburn, N., & Capilovitz, D. (1965). Reports on happiness. Chicago: Aldine.