Cheney, D. L. and Seyfarth, R. M. (2005) Constraints and preadaptations in the earliest stages of language evolution. The Linguistic Review , 22(2-4):135--159.

Cheney, D. L. and Seyfarth, R. M. (2005) Constraints and preadaptations in the earliest stages of language evolution. The Linguistic Review, 22(2-4):135--159.

Locke, Cost and complexity: Selection for speech and language, 2008	::
Swarup,Gasser, The Role of Anticipation in the Emergence of Language, 2007	::