McKenna S, Doward LC. Measuring quality of life in ankylosing spondylitis. Best Pract Res Clin Rheumatol. 2008 Jan 1;6(2):12-4.
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.