Roberts J, Price J, Nelson LM, Burchinal M, Hennon E, Barnes B. Receptive vocabulary, expressive vocabulary, and speech production of boys with fragile X syndrome in comparison to boys with Down syndrome. Am J Ment Retard. 2007 May 1;112:177-93.
Bradley RH, National Institute of Child Health and Human Development (NICHD) Early Child Care Research Network, McLeod LD. Child care and common communicable illnesses in children aged 37 to 54 months. Arch Pediatr Adolesc. 2003 Feb;157(2):196-200. doi: 10.1001/archpedi.157.2.196