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.