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Wulffaert J, Scholte EM, Dijkxhoorn YM, Bergman JE, van Ravenswaaij-Arts CM, van Berckelaer-Onnes IA.Wulffaert J, et al. Among authors: dijkxhoorn ym.J Dev Phys Disabil. 2009 Aug;21(4):301-313. doi: 10.1007/s10882-009-9143-y. Epub 2009 Jun 23.J Dev Phys Disabil. 2009.PMID: 19587801Free PMC article.