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.
Brodersen J, Meads DM, Kreiner S, Thorsen H, Doward LC, McKenna SP. Methodological aspects of differential item functioning in the Rasch model. J Med Econ. 2007;10:309-22.