Reference:
Ukoumunne OC, Wake M, Carlin J, Bavin EL, Lum J, Skeat J, Williams J, Conway L, Cini E, Reilly S. Profiles of language development in pre-school children: a longitudinal latent class analysis of data from the Early Language in Victoria Study. Child: Care, Health & Development 2012;38(3): 341—349.