Conning, A. M.,& Byrne, R. W.1984 Pointing to preschool children’s spatial competence: A study in natural settings. Journal of Environmental Psychology, 4, 165-175.
Emmorey, K., Tversky, B.,& Taylor, H. A.2000 Using space to describe space: Perspective in speech, sign, and gesture. Spatial Cognition and Computation, 2, 157-180.