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van Balen JA, Flikweert S, Wieringa-de Waard M, de jonge A, Wiersma T, Goudswaard AN.van Balen JA, et al.Ned Tijdschr Geneeskd. 2005 Feb 5;149(6):295-8.Ned Tijdschr Geneeskd. 2005.PMID: 15730036Dutch.