Ulbaek, I. (1998) The origin of language and cognition. In Hurford, J. R. and Studdert-Kennedy, M. and Knight C., editors, Approaches to the Evolution of Language: Social and Cognitive Bases . Cambridge: Cambridge University Press.

Ulbaek, I. (1998) The origin of language and cognition. In Hurford, J. R. and Studdert-Kennedy, M. and Knight C., editors, Approaches to the Evolution of Language: Social and Cognitive Bases. Cambridge: Cambridge University Press.

2005	-	Why talk: an Adaptationist Approach - Scott-Phillips	::
		Ulbaek, I., 1998, The origin of language and cognition, in Hurford, J. R., Studdert-Kennedy, M. and Knight, C. (eds.), Approaches to the evolution of language: Social and cognitive bases, Cambridge: Cambridge University Press, p.30-43
2004	-	Secret Agents: Synthetic Approaches to Language Evolution - Thomforde	::
		[27] I. Ulbaek. The origin of language and cognition. In J. Hurford, M. StuddertKennedy, and C. Knight, editors, Approaches to the Evolution of Language, pages 30--43. Cambridge University Press, 1998.