Reference:
Wake M, Tobin S, Girolametto L, Ukoumunne OC, Gold L, Levickis P, Sheehan J, Goldfeld S, Reilly S. Outcomes of population-based language promotion for slow-to-talk toddlers at ages 2 and 3 years: the Let’s Learn Language cluster randomised controlled trial. British Medical Journal 2011;343: d4741.