1. Babbie, E. (1992). The practice of social research (6th ed.). Belmont, CA: Wadsworth.
2. Barker, R. G. (1968). Ecological psychology. Stanford: Stanford University Press.
3. Boal, F. W., & Livingstone, D. N. (Eds.). (1989). The behavioural environment: Essays in reflection, application and re-evaluation. London and New York: Routledge.
4. Brown, L. (2009). Observational field research. Ithaca: Cornell University.
5. Bryman, A. (1988). Quantity and quality in social research. London and New York: Routledge.