Key points are not available for this paper at this time.
Lois Bloom, Patsy Lightbown, Lois Hood, Melissa Bowerman, Michael Maratsos, Michael P. Maratsos, Structure and Variation in Child Language, Monographs of the Society for Research in Child Development, Vol. 40, No. 2, Structure and Variation in Child Language (May, 1975), pp. 1-97
Bloom et al. (Thu,) studied this question.