Bruner, C. A., and J. E. Landaverde. “The Effects of Varyng the Spatial Localization of the Conditioned Stimulus in an autoshaping/Automaintenance Situations”. Mexican Journal of Behavior Analysis, vol. 11, no. 1 y 2, June 2011, pp. 11-20, doi:10.5514/rmac.v11.i1 y 2.25761.