Snowdon, C. T. (1999) An Empiricist View of Language Evolution and Development. In Barbara J. King, editor, The Origins of Language: What Nonhuman Primates Can Tell Us . School of American Research Press.

Snowdon, C. T. (1999) An Empiricist View of Language Evolution and Development. In Barbara J. King, editor, The Origins of Language: What Nonhuman Primates Can Tell Us. School of American Research Press.

2004	-	Human uniqueness, learned symbols and recursive thought - Hurford	::
		Snowdon, Charles T. 1999, ``An Empiricist View of Language Evolution and Development'', in The Origins of Language: What Nonhuman Primates Can Tell Us, edited by Barbara J. King, School of American Research Press, Santa Fe, New Mexico. pp.79-114.