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Williams SE, Blount RL, Walker LS.Williams SE, et al. Among authors: walker ls.J Pediatr Psychol. 2011 Jan;36(1):55-63. doi: 10.1093/jpepsy/jsq043. Epub 2010 May 19.J Pediatr Psychol. 2011.PMID: 20484330Free PMC article.