Wamble DE, Ciarametaro M, Houghton K, Ajmera M, Dubois RW. What's been the bang for the buck? Cost-effectiveness of health care spending across selected conditions in the US. Health Aff (Millwood). 2019 Jan;38(1):68-75. doi: 10.1377/hlthaff.2018.05158.
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.