1. Bruner, J. S., Goodnow, J., & Austin, G. (1956). A study of thinking. New York: Wiley.
2. Kendler, T. S., Kendler, H. H., & Learnard, B. (1962). Mediated responses to size and brightness as a function of age. American Journal of Psychology, 75, 571–586.
3. Ormrod, J. E. (2008). Human learning (5th ed.). Upper Saddle River, NJ: Pearson.
4. Rosch, E. H. (1978). Principles of categorization. In E. Rosch & B. Lloyd (Eds.), Cognition and categorization (pp. 27–48). Hillsdale, NJ: Erlbaum.
5. Ross, B. H., & Spalding, T. L. (1994). Concepts and categories. In R. J. Sternberg (Ed.), Handbook of perception and cognition (Vol. 12, pp. 119–148). New York: Academic.