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Farran, E.K. and Brown, J.H. and Cole, V.L. and Houston Price, C. and Karmiloff-Smith, Annette (2009) A longitudinal study of perceptual grouping by proximity, luminance and shape in infants at two, four and six months. European Journal of Developmental Science 2 (4), pp. 353-369. ISSN 1863-3811.