1. Bart, J., Fligner, M., & Notz, W. (1998). Sampling and statistical methods for behavioral ecologists. Cambridge: Cambridge University Press.
2. Cochran, W. (1977). Sampling techniques. Hoboken: Wiley.
3. Crook, J. H. (1964). The evolution of social organisation and visual communication in the weaver birds (Ploceinae). Behaviour, 10, 1–178.
4. Darwin, C. (1859). On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray.
5. Dewsbury, D. A. (2003). The 1973 Nobel Prize for physiology or medicine: Recognition for behavioral science? American Psychology, 58(9), 747–752.