1. Chomsky, N.A. (1975) Reflections on LAnguage, Pantheon
2. Hume, D. (1740) reprinted in David Hume on Human Nature and Understanding (Flew, A., ed.) (1962), pp. 167–285, Collier Books
3. Quine, W.V. (1960) Word and OBject, MIT Press
4. Spelke, E.S. (1988) in Thought WIthout LAnguage (Weiskrantz, L., ed.), pp. 168–184, Clarendon Press/Oxford University Press
5. Initial knowledge: six suggestions;Spelke;Cognition,1994